feat: add Google code retrieval across desktop CLI and MCP

docs/ROADMAP.md

@@ -105,6 +105,25 @@ Audit and measured priorities: [EMBEDDINGGEMMA2-AUDIT.md](EMBEDDINGGEMMA2-AUDIT.
 
 Completion requires recorded evidence; targets are not measured results.
 
+## 8. Source-code retrieval
+
+- [x] Shared code classification, strict lexical/ANN filtering before top-k,
+  expanded source/build formats, bounded overlapping passages and actual lines.
+- [x] Desktop Code scope, CLI `--code-only`, read-only MCP `code_only`, immutable
+  scope snapshots and code-format-preserving previews.
+- [x] Google's CodeRetrieval query instruction, explicit worker capabilities,
+  task-scoped vector cache and genuine CPU prompt/debug parity.
+- [x] Exact original source windows when Google's tokenizer normalizes text;
+  verified UTF-8 offsets, full tail coverage and actual token-budget checks.
+- [x] Schema-11 migration schedules unchanged source for re-extraction; tests
+  preserve ordinary documents and filename availability through the upgrade.
+- [x] Frozen 9-query real Google CPU regression with lexical comparison,
+  ordinary-document exclusion and exact MCP source excerpt verification.
+- [ ] Evaluate independent real repositories, more languages, overloaded
+  symbols, near-duplicate routines and queries with no relevant implementation.
+- [ ] Validate code search UI interaction on native Windows/macOS/Linux and
+  actual GPU hardware. Tiny CPU fixtures do not close those release gates.
+
 ## Completed foundation details
 
 - SQLite FTS5 with exact filename priority, text snippets and strict filters.