refine(task-executor): add Unimplemented Dependency Handling rule

[shinpr]

Summary

Adds an explicit Unimplemented Dependency Handling rule to the task-executor and task-executor-frontend agents (en + ja sources), plus a patch release.

When Pre-implementation Verification finds a dependency the task requires is absent or unimplemented, the executor previously had no defined branch — it could either over-eagerly block or invent a substitute. This rule makes the decision explicit and machine-checkable:

• Establish the contract first. The required contract is read from an already-read source (Design Doc / API spec / UI Spec / a Dependencies: deliverable read at Step 2). When the dependency is a Dependencies: deliverable that does not exist and no read source defines the contract, the contract is undeterminable → escalate as design_compliance_violation (a stand-in cannot preserve an undefined contract).
• A missing dependency is a stop condition only when preserving the required contract needs it and no local, reversible construct — a vertical slice, or a contract-preserving stub/adapter scoped to the Target Files — can stand in. A stand-in flagged by the Step 4 Core Mechanism Preservation Check does not qualify.
• Branch:
  • One or more local, reversible constructs preserve the contract and are interchangeable (no architectural trade-off between them) → proceed with one and record the integration handoff in Investigation Notes.
  • No construct preserves the contract, or two or more differ on an architectural trade-off (placement, dependency direction / component hierarchy / data flow direction, contract shape) → escalate as design_compliance_violation, populating every required field (details.design_doc_expectation, details.actual_situation, details.why_cannot_implement, details.attempted_approaches[], claude_recommendation).

Reuses the existing design_compliance_violation escalation type — no new enum value. Consistent with the existing Iron Rule and Step 4 Core Mechanism Preservation Check.

Changes

• 7fd38a5 — en sources (agents-en/task-executor.md, agents-en/task-executor-frontend.md)
• d0c1da5 — ja sources mirrored, matching the files' established tone and terminology (代替, 垂直スライス, Step4 中核メカニズム保全チェック, 鉄則; Design Doc / UI Spec / Target Files / Investigation Notes kept in English per file convention; "preserve" unified as 保全)
• 6c2e918 — release 1.25.1 (package.json, CHANGELOG.md)

Scope notes

Edits are in the canonical agents-en/ and agents-ja/ sources; the active .claude/agents/ is sync-generated by scripts/set-language.js. check:skills-index passes (28 skills consistent across en/ja).

🤖 Generated with Claude Code