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>

package.json

@@ -93,11 +93,15 @@
     "fflate": "0.8.2",
     "figures": "6.1.0",
     "fuse.js": "7.1.0",
+    "graphology": "^0.26.0",
+    "graphology-operators": "^1.6.0",
     "get-east-asian-width": "1.5.0",
     "google-auth-library": "9.15.1",
     "https-proxy-agent": "7.0.6",
     "ignore": "7.0.5",
+    "graphology-pagerank": "^1.1.0",
     "indent-string": "5.0.0",
+    "js-tiktoken": "^1.0.16",
     "jsonc-parser": "3.3.1",
     "lodash-es": "4.18.1",
     "lru-cache": "11.2.7",
@@ -117,10 +121,12 @@
     "strip-ansi": "7.2.0",
     "supports-hyperlinks": "3.2.0",
     "tree-kill": "1.2.2",
+    "tree-sitter-wasms": "^0.1.12",
     "turndown": "7.2.2",
     "type-fest": "4.41.0",
     "undici": "7.24.6",
     "usehooks-ts": "3.1.1",
+    "web-tree-sitter": "^0.25.0",
     "vscode-languageserver-protocol": "3.17.5",
     "wrap-ansi": "9.0.2",
     "ws": "8.20.0",