feat(repo-map): add budgeted local code understanding

[luoye520ww]

Summary

Add a first-class repo_map tool that gives Kun a compact, query-ranked view of an unfamiliar local codebase before broad read/grep passes.

Changes

• discover tracked and non-ignored workspace files through Git, with a safe filesystem fallback for non-Git folders
• skip generated/dependency/nested-repository directories and enforce a configurable scan budget
• extract symbols and imports across common languages, including camelCase/snake/kebab tokenization
• rank files with BM25-style relevance, entrypoint/core-path signals, and Git working-tree/recent-commit recency
• cache short-lived indexes by workspace/target/Git HEAD and expose cache/backend/truncation diagnostics
• make repo_map available to normal, plan, and read-only subagent tool policies
• add real-filesystem tests for ranking, symbol/import extraction, ignored directories, and cache reuse

Tests

• npm.cmd --prefix kun test -- src/adapters/tool/builtin-repo-map-tool.test.ts src/adapters/tool/builtin-tool-types.test.ts
• npm.cmd --prefix kun run typecheck
• npm.cmd --prefix kun run build
• focused ESLint on changed files
• smoke on this repository: 1,073 Git-visible files indexed in about 2.4s; MCP/runtime files ranked first for runtime mcp reconnect reliability