Phase 1b: add deterministic code KG indexer

[edheltzel]

Summary

• Adds recall index [path] backed by a deterministic web-tree-sitter indexer.
• Captures function/class/method declarations plus exported arrow/function-expression consts.
• Persists repo-relative code nodes/edges with stable kind:relpath:qualified_name:start_line:start_col IDs, real caller attribution, deterministic resolution, and a re-link pass.
• Pins web-tree-sitter@0.26.9 and tree-sitter-typescript@0.23.2.

Notes

• This PR intentionally consumes the code KG schema from Phase 1a: code-KG schema + 15→16 migration #199 / the design DDL; production schema DDL is not redefined here.

Verification

• bun test tests/lib/code-indexer.test.ts — 5 pass.
• bun run lint — pass.
• bun test — 1197 pass, 0 fail.
• bun run build — pass.
• Actual Recall src/ indexing against an in-memory DB using the design DDL: 67 files, 756 nodes, 4905 edges, 3590 non-module caller call edges, 177 extracted module import edges.

Closes #200