refactor: factor tree-sitter symbol extraction into helpers (go, typescript)

[saldestechnology]

Summary

Behavior-preserving refactor that reduces the fan-out/complexity of the two
long tree-sitter symbol extractors by factoring their inline
Symbol/Edge/import construction out of the QueryCursor match loop into
private free helpers, mirroring the reference pattern already used in
src/parser/rust.rs. The main loops are now pure dispatch.

Changes

src/parser/go.rs

• New push_go_import_edges(...) — the import-edge branch.
• New build_go_symbol(...) — the per-match Symbol construction body.
• build_signature / extract_docstring converted from methods to free
  build_go_signature / extract_go_docstring (thread &Query instead of &self).

src/parser/typescript.rs

• New push_ts_import(...) and build_ts_symbol(...).
• Reuses the existing free helpers (build_signature, extract_jsdoc,
  is_exported, extract_import_names, extract_import_source).

Fan-out (via ctx complexity)

function	before	after
go.rs::extract_symbols	61	17
typescript.rs::extract_symbols	48	25

Correctness

Pure refactor — no test expectations changed.

• cargo test — all pass (269 lib + integration suites green)
• cargo clippy -- -D warnings — clean
• ctx check — no architecture violations
• New duplication: 0