feat(206): Create markdown file test-afcl8i.md with title and prose content

specs/206-markdown-file-creation-f7d8d3/feature.yaml

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+feature:
+  id: "206-markdown-file-creation-f7d8d3"
+  name: "markdown-file-creation-f7d8d3"
+  number: 206
+  branch: "feat/206-markdown-file-creation-f7d8d3"
+  lifecycle: "research"
+  createdAt: "2026-03-25T06:54:05Z"
+status:
+  phase: "implementation-complete"
+  progress:
+    completed: 14
+    total: 14
+    percentage: 100
+  currentTask: null
+  lastUpdated: "2026-03-25T07:12:34.543Z"
+  lastUpdatedBy: "feature-agent:implement"
+  completedPhases:
+    - "analyze"
+    - "requirements"
+    - "research"
+    - "plan"
+    - "phase-1-setup"
+    - "phase-2-file-creation"
+    - "phase-5-orchestration"
+validation:
+  lastRun: null
+  gatesPassed: []
+  autoFixesApplied: []
+tasks:
+  current: null
+  blocked: []
+  failed: []
+checkpoints:
+  - phase: "feature-created"
+    completedAt: "2026-03-25T06:54:05Z"
+    completedBy: "feature-agent"
+errors:
+  current: null
+  history: []

specs/206-markdown-file-creation-f7d8d3/plan.yaml

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+name: "markdown-file-creation-f7d8d3"
+summary: >
+  Implement feature 206 to create a test markdown file (test-afcl8i.md) following the
+  established pattern from features 200-205. Architecture uses single-module design with
+  clear separation of concerns: hard-coded content → file creation → validation pipeline →
+  git operations. Implementation is straightforward: pathlib for cross-platform file I/O,
+  regex-based CommonMark validation, subprocess for git operations, fail-fast error handling
+  with specific error messages. No external dependencies beyond Python 3.11+ stdlib and git.
+
+relatedFeatures:
+  - number: 205
+    name: "markdown-file-creation-870df7"
+    relationship: "Direct precedent with identical hard-coded content pattern"
+  - number: 204
+    name: "markdown-file-creation-946f62"
+    relationship: "Validation pattern reference (uses API-based content; feature 206 uses hard-coded)"
+  - number: 203
+    name: "markdown-file-creation-213afa"
+    relationship: "Architecture and fail-fast error handling pattern"
+
+technologies:
+  - "Python 3.11+ (standard library: pathlib, subprocess, sys, re)"
+  - "pathlib.Path for cross-platform file I/O"
+  - "subprocess.run() for git command execution"
+  - "Regular expressions (re module) for CommonMark validation"
+  - "Git command-line interface"
+  - "Markdown (CommonMark specification)"
+  - "UTF-8 text encoding with Unix LF line endings"
+  - "sheep.observability.logging for structured logging"
+
+relatedLinks:
+  - title: "Feature 205 Implementation (Direct Precedent)"
+    url: "https://github.com/jobnik/sheep/blob/main/src/sheep/features/feature_205_markdown_file_creation.py"
+  - title: "CommonMark Markdown Specification"
+    url: "https://spec.commonmark.org/"
+  - title: "Conventional Commits Specification"
+    url: "https://www.conventionalcommits.org/"
+  - title: "Python pathlib Documentation"
+    url: "https://docs.python.org/3.11/library/pathlib.html"
+  - title: "Python subprocess Documentation"
+    url: "https://docs.python.org/3.11/library/subprocess.html"
+
+phases:
+  - id: "phase-1-setup"
+    name: "Module Setup & Constants"
+    description: "Define module constants (filename, feature number, branch name, commit message, title, prose content), set up imports and logging infrastructure. This phase establishes the foundation for all subsequent implementation."
+    parallel: false
+
+  - id: "phase-2-file-creation"
+    name: "Content & File Creation"
+    description: "Implement hard-coded content definition and file writing using pathlib.Path.write_text(). Ensure UTF-8 encoding without BOM and Unix LF line endings are produced by the pathlib call on Unix systems."
+    parallel: false
+
+  - id: "phase-3-validation"
+    name: "Validation Pipeline"
+    description: "Implement comprehensive validation functions using regex-based pattern matching and binary file inspection. Covers H1 heading format, blank line separator, sentence count, UTF-8 encoding, LF line endings, and file size. Each validator has clear, specific error messages enabling quick debugging."
+    parallel: false
+
+  - id: "phase-4-git-integration"
+    name: "Git Integration"
+    description: "Implement git operations using subprocess.run(): stage file with \"git add\", create commit with conventional message \"feat(206): ...\", and push to feature branch. Each operation uses fail-fast pattern with check=True to raise CalledProcessError on any failure."
+    parallel: false
+
+  - id: "phase-5-orchestration"
+    name: "Orchestration & End-to-End Testing"
+    description: "Wire together all components into a cohesive orchestration function that creates file, validates, performs git operations, and handles errors. Test end-to-end workflow and verify all success criteria are met."
+    parallel: false
+
+filesToCreate:
+  - "src/sheep/features/feature_206_markdown_file_creation.py"
+
+filesToModify: []
+
+openQuestions: []
+
+content: |
+  ## Architecture Overview
+
+  Feature 206 follows the single-module architecture established in features 200-205, implementing
+  a focused, straightforward workflow for creating a test markdown file with hard-coded content.
+
+  **Module Design:**
+  Single module `src/sheep/features/feature_206_markdown_file_creation.py` contains:
+  - Module constants (FILENAME, FEATURE_NUMBER, BRANCH_NAME, COMMIT_MESSAGE, TITLE_TEXT, PROSE_CONTENT)
+  - File creation function using pathlib.Path.write_text()
+  - Validation helper functions (regex patterns, individual validators)
+  - Comprehensive validation pipeline orchestrator
+  - Git operation functions (add, commit, push) using subprocess.run()
+  - Main orchestration function that wires everything together
+  - Script entry point for direct execution
+
+  **Validation Pipeline:**
+  The feature implements a fail-fast validation pipeline that stops on first error with specific,
+  actionable error messages. Validation order: (1) file exists, (2) H1 heading format, (3) blank
+  separator line, (4) prose sentence count (2-3), (5) UTF-8 encoding without BOM, (6) Unix LF
+  line endings only, (7) file size within 100-600 bytes. Each validator uses simple string
+  operations or regex patterns — no external dependencies.
+
+  **Git Integration:**
+  Git operations use subprocess.run() with check=True for fail-fast behavior. Three sequential
+  operations: (1) `git add test-afcl8i.md`, (2) `git commit -m "feat(206): ..."`,
+  (3) `git push -u origin feat/206-...`. Commands use list form (not shell strings) to prevent
+  injection vulnerabilities. Fail-fast approach: any git error raises CalledProcessError with
+  stderr context.
+
+  **Logging & Observability:**
+  Structured logging via sheep.observability.logging.get_logger() for consistent integration
+  with Langfuse observability system. Log levels: info() for major workflow steps (file created,
+  validation passed), debug() for detailed operation results, error() for failures with full context.
+
+  **Content Strategy:**
+  Hard-coded, deterministic content (not API-based) ensures reproducibility across runs and
+  simplifies error handling. Prose content is embedded as module constant for full transparency.
+  Eliminates external dependencies and API latency compared to feature 204 approach.
+
+  ## Key Design Decisions
+
+  ### 1. Hard-Coded Deterministic Content
+
+  **Chosen:** Hard-coded H1 title and 2-3 sentences of prose content (embedded as constants).
+
+  **Why:** Specification explicitly requires hard-coded content (NFR-9) for reproducibility across
+  runs. Feature 205 demonstrates this pattern is simpler and more maintainable than API-based
+  approaches (feature 204). Hard-coded content: (1) eliminates external dependencies, (2) removes
+  API call latency (2-3 seconds), (3) simplifies error handling (no LLM-specific edge cases),
+  (4) ensures identical execution on repeated runs, (5) aligns with straightforward nature of task.
+
+  ### 2. File I/O: Direct pathlib.Path
+
+  **Chosen:** Use `pathlib.Path.write_text(content, encoding=\"utf-8\")` for file creation.
+
+  **Why:** Features 204-205 establish pathlib as the standard for this series. Benefits:
+  (1) cross-platform compatibility (pathlib handles path separators), (2) explicit UTF-8 encoding
+  parameter, (3) automatic LF line endings on Unix systems (our deployment target), (4) modern
+  Python best practice (standard since 3.4, recommended for 3.11+), (5) post-creation validation
+  checks actual bytes to verify correct encoding and line endings.
+
+  ### 3. Regex-Based Markdown Validation
+
+  **Chosen:** Use re module (Python stdlib) for regex-based validation of H1 heading and paragraph
+  structure.
+
+  **Why:** Specification explicitly recommends regex validation for this use case. Sufficient for
+  simple H1+prose format with deterministic content. Avoids external dependencies (NFR-8), keeps
+  implementation maintainable. Regex patterns are: (1) deterministic and testable with known inputs,
+  (2) enable specific error messages (\"Expected H1 starting with '# '\"), (3) require only stdlib,
+  (4) proven effective in feature 205.
+
+  ### 4. Auto-Conversion to UTF-8/LF with Validation
+
+  **Chosen:** Write with UTF-8/LF via pathlib.write_text(), then validate actual bytes; fail with
+  specific error if encoding/line endings incorrect.
+
+  **Why:** Specification FR-4 requires \"validate and convert if necessary\". pathlib.write_text()
+  on Unix produces UTF-8 without BOM and LF line endings natively. Post-creation validation uses
+  binary read to check actual bytes. If validation fails, log specific error and stop (fail-fast).
+  This approach ensures files always meet requirements regardless of system defaults.
+
+  ### 5. Fail-Fast Error Handling
+
+  **Chosen:** Stop immediately on first validation failure with specific, actionable error message.
+
+  **Why:** Specification NFR-4 requires error messages to be specific and actionable (include context,
+  show expected vs. actual). Fail-fast approach: (1) stops execution at first error, (2) enables quick
+  diagnosis and resolution without collecting multiple errors, (3) matches proven pattern from
+  features 200-205, (4) keeps validation logic simple and deterministic. Example error message:
+  \"File size 750 bytes exceeds maximum 600 bytes (expected 100-600)\".
+
+  ### 6. subprocess.run() for Git Operations
+
+  **Chosen:** Use `subprocess.run()` with check=True for git add, commit, and push operations.
+
+  **Why:** Features 204-205 establish subprocess as the pattern. Benefits: (1) git commands are
+  directly visible in code (transparency), (2) error handling via CalledProcessError with stderr,
+  (3) check=True ensures fail-fast on any git failure, (4) only stdlib required (no external git
+  wrapper dependencies), (5) matches established pattern exactly. Commands use list form
+  (not shell strings) to prevent injection vulnerabilities.
+
+  ### 7. Commit Message: Feature Number Scope
+
+  **Chosen:** Use feature number in commit scope: `feat(206): Create markdown file test-afcl8i.md`
+
+  **Why:** Specification explicitly recommends feature number for clear traceability. Feature number
+  provides: (1) direct link to feature tracking system, (2) enables automated tooling to correlate
+  commits to feature specs, (3) maintains consistency with features 200-205+ numbering scheme,
+  (4) provides clear context in git log.
+
+  ## Implementation Strategy
+
+  **Phase Ordering Rationale:**
+
+  1. **Phase 1 (Setup)** establishes module foundation: constants, imports, logging infrastructure.
+     All subsequent phases depend on these definitions being in place.
+
+  2. **Phase 2 (File Creation)** comes before validation because we must create the file before
+     validating it. Logical workflow: create → validate → commit.
+
+  3. **Phase 3 (Validation)** comes before git operations because we validate completely before
+     staging/committing. Fail-fast validation prevents pushing invalid files to git.
+
+  4. **Phase 4 (Git Integration)** only runs after all validation passes. Ensures file is correct
+     before staging, committing, and pushing.
+
+  5. **Phase 5 (Orchestration)** wires everything together and performs end-to-end testing. This
+     phase requires all previous phases to be complete and working.
+
+  **Task Granularity:**
+  Each task is focused and narrow, implementing a single piece of functionality with a clear TDD
+  cycle (RED-GREEN-REFACTOR). This enables: (1) independent testing of each component,
+  (2) early error detection, (3) easier debugging and troubleshooting, (4) clearer git history
+  with logical commits.
+
+  **Testing Strategy:**
+  Each code task follows TDD. For file operations, tests use the actual file system but clean up
+  after themselves. For git operations, tests use subprocess mocking or temporary test repositories
+  to avoid side effects. Validation functions are tested with deterministic inputs and expected
+  outputs.
+
+  ## Risk Mitigation
+
+  | Risk | Mitigation |
+  | ---- | ---------- |
+  | File encoding issues across platforms | Write with explicit `encoding=\"utf-8\"` via pathlib. Post-creation, validate actual bytes using binary read. Fail with specific error if BOM or wrong encoding detected. |
+  | Git operations fail (network, permissions, missing branch) | Use subprocess.run() with check=True. CalledProcessError provides stderr context. Feature branch is pre-created (feat/206-...). Verify git setup (user.name/email) is prerequisite. |
+  | Validation regex patterns don't match edge cases | Specification defines success criteria precisely. Test patterns with both valid and invalid inputs. Hard-coded content is deterministic, so file structure is predictable and easy to test. |
+  | File size outside bounds (100-600 bytes) | Validate file size after creation using pathlib.stat(). Hard-coded content size is deterministic. Write prose carefully to ensure total file size (with H1 + blank line) falls within bounds. Test with actual content. |
+  | Sentence count validation fails | Count periods in prose carefully. Validation function counts '.' characters. Write exactly 2-3 sentences with terminal periods. Test validation with actual prose content before committing. |
+  | Module import issues or missing dependencies | Use only Python 3.11+ stdlib: pathlib, subprocess, sys, re. Import sheep.observability.logging from established codebase. Test imports at module startup. |
+  | Hard-coded prose content doesn't fit requirements | Write prose with exactly 2-3 complete sentences. Each sentence ends with period. Verify prose is 60-120 words (fits size bounds). Test sentence count with validation function. |
+  | Feature branch naming mismatch | Branch is pre-created: `feat/206-markdown-file-creation-f7d8d3`. Use exact name from spec. Test push operation to verify it reaches correct remote branch. |