feat: add Codebase Intelligence — repo map with PageRank-ranked structural summaries

Add a new module that builds a structural map of the repository by parsing
source files with tree-sitter, building a cross-file reference graph
weighted by IDF, ranking files with PageRank, and rendering a
token-budgeted summary of the most important files and their signatures.

Stage 1 — Core module (src/context/repoMap/):
  Symbol extraction via web-tree-sitter WASM, IDF-weighted reference graph
  via graphology, PageRank ranking, token-budgeted rendering via js-tiktoken
  cl100k_base, disk cache with mtime invalidation. Supports TypeScript,
  JavaScript, and Python. 10 tests.

Stage 2 — RepoMap tool (src/tools/RepoMapTool/):
  buildTool wrapper registered in src/tools.ts. Read-only, concurrency-safe.
  Supports focus_files, focus_symbols, and max_tokens parameters. 9 tests.

Stage 3 — Integration:
  Auto-injection into session context behind REPO_MAP feature flag (off by
  default). /repomap slash command with --tokens, --focus, --stats, and
  --invalidate flags. User-facing docs in docs/repo-map.md. 13 tests.

With the flag off, the system context is byte-identical to previous behavior.

Dependencies: web-tree-sitter, tree-sitter-wasms, graphology,
graphology-pagerank, graphology-operators, js-tiktoken

Tests: 32 new, 621 total passing, 0 failures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -154,6 +154,7 @@ Advanced and source-build guides:
 - **Images**: URL and base64 image inputs for providers that support vision
 - **Provider profiles**: Guided setup plus saved `.openclaude-profile.json` support
 - **Local and remote model backends**: Cloud APIs, local servers, and Apple Silicon local inference
+- **Codebase intelligence (repo map)**: Structural map of the repository ranked by PageRank importance, auto-injected into context when the `REPO_MAP` flag is enabled. Inspect with `/repomap`. See [docs/repo-map.md](docs/repo-map.md) for details.
 
 ## Provider Notes