fix: preserve builder sources and Go receiver method symbols

[Helweg]

Fix two demonstrated acquisition/declaration defects

Separate from the completed exploratory study in #422; this branch starts at its frozen candidate commit 969fd34. No study tasks, configurations, scores or evidence artifacts are changed, and the consumed cohort was not rerun.

Source policy

• Replace arbitrary build substring matching with a dash/underscore-delimited build token.
• Share the generated-directory pattern catalog across default excludes and Git-ignore-style automatic filtering.
• Preserve clap_builder/, builder/, rebuild/, build.rs and build.gradle; retain build/, _build/, app-build/, cmake-build-debug/ and mixed-delimiter output directories.
• Keep dependency/cache/hidden guards, upstream .gitignore, explicit user exclusions and opt-in boundaries effective for indexing and watcher filters. An explicitly configured **/*build*/** remains authoritative.

Go declaration extraction and cached upgrade

• Recognize Go grammar field_identifier method names in the existing extractor; no additional parsing/allocations or other-language widening.
• Correct value/pointer/generic receiver methods with void, scalar, slice, map/compound and named returns, rather than storing return-type names or omitting methods.
• Upgrade the existing symbol-extractor version so ordinary non-forced indexing reparses unchanged cached declarations/chunks. No new persistence format or migration abstraction.
• Regression coverage checks exact declaration names/ranges and meaningful chunks, plus reopening/upgrading a previous-version catalog in both hybrid and structural modes. Remove incidental current-version-number assertions rather than re-pin them.

Runtime verification

Before the fix, a fresh synthetic collector omitted builder/rebuild sources and native receiver symbols contained int/error instead of method names.

After rebuilding, an actual SDK client launched the built MCP CLI on another fresh synthetic project. implementation_lookup resolved Rust WidgetBlueprint under clap_builder/ and Go Flush, Size, Check, List under rebuild/ with correct files/source. Generated/hidden/dependency and Git-ignored sentinels returned not_found, as did the false int alias. After seeding a previous-version Size -> int catalog, ordinary index_codebase(force:false) repaired the unchanged source and removed the false alias.

Checks

• npm run build — passed, including rebuilt Rust/NAPI and built-CLI smoke.
• npm run typecheck — passed.
• npm run lint — passed.
• npx vitest run — 142 test files passed, 1 skipped; 2,638 tests passed, 6 skipped.
• Fresh synthetic built-MCP SDK smoke — passed for discovery, exact lookup, exclusions and non-forced cached migration.

No Kotlin support, retrieval-ranking tuning, embedding replacement or fresh competitive claim is included.