feat(core): Go callee extraction + Rust language support

[prosdev]

Summary

• Rust scanner: Full extraction — functions, structs, enums, traits, impl methods, imports, callees, doc comments (~530 lines)
• Rust patterns: try operator, match expression, unsafe block, impl/trait definitions
• Go callees: walkCallNodes for functions and methods — dev_refs now traces Go call chains
• Go patterns: error handling (if err != nil), goroutines, defer, channels
• Pipeline wiring: .go/.rs in EXTENSION_TO_LANGUAGE, rust in supportedLanguages, copy-wasm, test-utils
• Fix: .go was missing from EXTENSION_TO_LANGUAGE — Go patterns never fired

Rust scanner highlights

• impl_item.type field for method naming (works for both impl Type and impl Trait for Type)
• Functions inside mod blocks captured (query matches at any depth, parent-chain filter excludes only impl methods)
• Generic type param stripping via split('<')[0]: handles Container<T>, HashMap<String, Vec<u8>>, Wrapper<Option<T>>
• Macros intentionally excluded from callees (explicit macro_invocation early return in walkCallNodes)
• Doc comments via /// prefix, attributes (#[derive]) skipped during backward walk
• Malformed file resilience: returns empty, no crash

Code review history

• Review 1 (general): Misleading macro comment → fixed (actual skip added). Orphaned JSDoc → fixed. Attribute comment → added.
• Review 2 (Rust expert): mod block support missing (CRITICAL) → fixed (removed source_file anchoring, added parent-chain filter). Greedy generic stripping → fixed (split('<')[0]). Both fixes have dedicated tests.
• Review 3 (final pass): APPROVED. All findings verified fixed, no regressions.

Test plan

Automated (1758 tests, all passing)

• 14 Step 0 grammar validation tests (permanent reference for node names)
• 25 Rust scanner tests: functions, structs, enums, traits, methods, callees, generics, closures, macros, doc comments, async, mod blocks, nested generics, malformed, generated
• 6 Go callee tests: functions, methods, full selector names, line numbers, dedup, no callees on structs
• 2 new pattern matcher tests: resolveLanguage('.go') and resolveLanguage('.rs')
• Full suite: 1758 passed, 39 skipped
• Lint + typecheck clean

Manual verification — Rust (BurntSushi/ripgrep)

Cloned --depth 1, ran local build against it.

Command	Result
dev index	119 files, 3,226 components indexed in 8.5s. No crash.
dev map --depth 2	Crate structure captured correctly: crates/searcher/, crates/printer/, crates/core/, etc.
dev refs "Searcher"	Found Searcher.new at crates/searcher/src/searcher/mod.rs:632. Callees: SearcherBuilder::new().build, SearcherBuilder::new.
dev search "grep pattern matching"	10 results including GlobStrategic.is_match, grep-regex README, Glob.compile_matcher. Semantic search works on Rust code.

Note: Hot paths show 0 refs because tree-sitter callees don't resolve target files (no file field). This is a known limitation — the dependency graph only has edges when callees include file paths. Cross-file resolution for tree-sitter languages is tracked as future work.

Manual verification — Go (cli/cli)

Cloned --depth 1, ran local build against it.

Command	Result
Scan	830 files, 5,933 components scanned successfully in 3.2s.
dev index	Failed — Antfly Linear Merge choked on 5,933 docs: decoding request: json: string unexpected end of JSON input. Scanner works, Antfly batch size is the bottleneck.
NewCmdRoot callees	126 callees extracted including f.Config, fmt.Errorf, heredoc.Doc, versionCmd.Format, cmdutil.IsAuthCheckEnabled. Full selector text preserved.
Scale test (359 Go files)	2,488 docs, 1,541 with callees, 16,520 total callee references. Go callee extraction works at scale.

Note: Antfly Linear Merge fails at ~6k docs. Tracked in scratchpad. Fix options: batch into chunks, raise Antfly limit, or stream. This blocks full indexing of medium-large repos but does not affect the scanner itself.

Known limitations (documented in scratchpad)

1. Antfly batch size limit (~6k docs) blocks indexing large repos
2. Rust/Go callees don't resolve target files (no cross-file edges in dependency graph)
3. //! inner doc comments and /** */ block doc comments not extracted (v1)
4. Trait default method bodies not extracted
5. #[cfg(test)] inline test modules not detected as test files

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