[Go] Add code-graph extractor

[theDakshJaitly]

Target branch: main

Goal

Add a Go extractor against the frozen LanguageExtractor interface. The first version should model common package structure, declarations, and call relationships using only syntax available in an individual Go source file.

Scope

• Detect .go files as go.
• Vendor and register a compatible Tree-sitter Go WASM grammar.
• Emit a file node and containment tree.
• Extract functions, receiver methods, structs, interfaces, fields, package variables, and constants.
• Capture receiver-aware qualified names and function signatures.
• Emit imports, calls, containment, type references, and instantiation references when syntax makes them explicit.
• Leave cross-file and cross-package targets unresolved through targetName.

Required changes

• Add src/graph/extraction/languages/go.ts.
• Register the extractor in src/graph/extraction/languages/index.ts.
• Register .go and the grammar filename in src/graph/extraction/grammars.ts.
• Add the grammar WASM under src/graph/wasm/ and document its source, version, and license.
• Add a representative Go fixture and focused extractor tests.

Acceptance criteria

• The extractor implements the frozen LanguageExtractor interface without changing it.
• Extraction is pure, deterministic, and limited to one file.
• Node ids use the shared line-independent generator.
• Tests cover packages, functions, receiver methods, structs, interfaces, fields, constants, containment, imports, calls, and explicit instantiation.
• Receiver methods have stable qualified names that distinguish their owning type.
• Cross-file references remain unresolved for the engine to bind.
• Unsupported or malformed syntax does not crash graph construction.
• npm run typecheck, npm test, and npm run build pass.
• The packed build contains the Go grammar WASM.

Out of scope

• Implicit interface-satisfaction analysis.
• Build-tag evaluation, module downloading, or go list execution.
• Gin, Echo, or other framework semantics.
• Changes to identity, reconciliation, schema, or grounding semantics.

Contributor references

• Extending the code graph
• src/graph/extraction/languages/typescript.ts
• src/graph/__tests__/extractor.test.ts

Contributor workflow

git switch main
git pull
git switch -c feat/go-code-graph-extractor

Open the pull request with base branch main.

[abhinav-phi]

Hi @theDakshJaitly,

I'd like to work on this issue. If it's still available, could you please assign it to me?

Thanks!

[0xmohit]

This is done in #133. @theDakshJaitly

[abhinav-phi]

Noting for tracking: this looks covered by open PR #133 feat(graph): add Go language extractor by @0xmohit (branch feat/go-code-graph-extractor). Keeping this open until #133 merges, then it can close as completed. Thanks!