feat: add flake-aware Nix language support

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Added
 
+- **Nix support** (flake-aware): `.nix` files are parsed via the `nix` tree-sitter grammar shipped with `tree-sitter-language-pack`. Top-level and nested attrset bindings become `Function` nodes with flattened dotted names (e.g. `packages.default`, `devShells.default`). In `flake.nix`, `inputs.<name>.url = "..."` strings emit `IMPORTS_FROM` edges to the URL; `import <path>` and `callPackage <path> <args>` applications in any `.nix` file emit `IMPORTS_FROM` edges (relative paths are resolved against the caller's directory). Adds 7 tests (`TestNixParsing`) and fixtures `tests/fixtures/sample.nix`, `tests/fixtures/sample_module.nix`.
 - **GDScript support** (Godot): `.gd` files are parsed via the `gdscript` tree-sitter grammar shipped with `tree-sitter-language-pack`. Extracts inner classes (`class Name:`), the file-level `class_name` identity, functions (including `static func`), `extends` parent class as an IMPORTS_FROM edge, direct calls (`call`) and method calls (`attribute_call`). Adds 10 tests and `tests/fixtures/sample.gd`.
 
 ## [2.3.2] - 2026-04-14

CLAUDE.md

@@ -15,7 +15,7 @@ When using code-review-graph MCP tools, follow these rules:
 ## Architecture
 
 - **Core Package**: `code_review_graph/` (Python 3.10+)
-  - `parser.py` — Tree-sitter multi-language AST parser (19 languages including Vue SFC, Solidity, Dart, R, Perl, Lua + Jupyter/Databricks notebooks)
+  - `parser.py` — Tree-sitter multi-language AST parser (20 languages including Vue SFC, Solidity, Dart, R, Perl, Lua, Nix + Jupyter/Databricks notebooks)
   - `graph.py` — SQLite-backed graph store (nodes, edges, BFS impact analysis)
   - `tools.py` — 22 MCP tool implementations
   - `main.py` — FastMCP server entry point (stdio transport), registers 22 tools + 5 prompts

README.md

@@ -104,13 +104,13 @@ Large monorepos are where token waste is most painful. The graph cuts through th
   <img src="diagrams/diagram6_monorepo_funnel.png" alt="Next.js monorepo: 27,732 files funnelled through code-review-graph down to ~15 files — 49x fewer tokens" width="80%" />
 </p>
 
-### 23 languages + Jupyter notebooks
+### 24 languages + Jupyter notebooks
 
 <p align="center">
-  <img src="diagrams/diagram9_language_coverage.png" alt="19 languages organized by category: Web, Backend, Systems, Mobile, Scripting, plus Jupyter/Databricks notebook support" width="90%" />
+  <img src="diagrams/diagram9_language_coverage.png" alt="24 languages organized by category: Web, Backend, Systems, Mobile, Scripting, Config (Nix), plus Jupyter/Databricks notebook support" width="90%" />
 </p>
 
-Full Tree-sitter grammar support for functions, classes, imports, call sites, inheritance, and test detection in every language. Includes Zig, PowerShell, Julia, and Svelte SFC support. Plus Jupyter/Databricks notebook parsing (`.ipynb`) with multi-language cell support (Python, R, SQL), and Perl XS files (`.xs`).
+Full Tree-sitter grammar support for functions, classes, imports, call sites, inheritance, and test detection in every language. Includes Zig, PowerShell, Julia, Svelte SFC, and flake-aware Nix support. Plus Jupyter/Databricks notebook parsing (`.ipynb`) with multi-language cell support (Python, R, SQL), and Perl XS files (`.xs`).
 
 ---
 
@@ -192,7 +192,7 @@ The blast-radius analysis never misses an actually impacted file (perfect recall
 | Feature | Details |
 |---------|---------|
 | **Incremental updates** | Re-parses only changed files. Subsequent updates complete in under 2 seconds. |
-| **23 languages + notebooks** | Python, TypeScript/TSX, JavaScript, Vue, Svelte, Go, Rust, Java, Scala, C#, Ruby, Kotlin, Swift, PHP, Solidity, C/C++, Dart, R, Perl, Lua, Zig, PowerShell, Julia, Jupyter/Databricks (.ipynb) |
+| **24 languages + notebooks** | Python, TypeScript/TSX, JavaScript, Vue, Svelte, Go, Rust, Java, Scala, C#, Ruby, Kotlin, Swift, PHP, Solidity, C/C++, Dart, R, Perl, Lua, Zig, PowerShell, Julia, Nix, Jupyter/Databricks (.ipynb) |
 | **Blast-radius analysis** | Shows exactly which functions, classes, and files are affected by any change |
 | **Auto-update hooks** | Graph updates on every file edit and git commit without manual intervention |
 | **Semantic search** | Optional vector embeddings via sentence-transformers, Google Gemini, MiniMax, or any OpenAI-compatible endpoint (real OpenAI, Azure, new-api, LiteLLM, vLLM, LocalAI) |