feat(go): Add Go stdlib extraction tool for registry generation (PR-02)

[shivasurya]

Summary

• Add tools/internal/goextract package implementing Extractor for walking $GOROOT/src and extracting the full exported API surface of Go stdlib packages via go/parser and go/ast
• Extract functions (signatures, params, returns, generics, variadic, methods), types (struct/interface/alias with fields and methods), constants (iota detection), and package-level variables with docstrings and deprecation markers
• Generate per-package JSON files ({pkg}_stdlib.json) and manifest.json with SHA256 checksums and aggregate statistics (186 packages from Go 1.26 stdlib)
• Add CLI entry point tools/generate_go_stdlib_registry.go with --go-version, --output-dir, and --goroot flags
• Achieve 100% test coverage with 40+ unit tests and integration tests against real Go 1.26 stdlib

Test plan

• go build ./... passes with zero errors
• golangci-lint run ./... reports 0 issues
• go test ./tools/internal/goextract/ — 100% coverage, all tests pass
• Integration test extracts 186 packages from Go 1.26 stdlib, verifies fmt.Println variadic, slices.Sort generic, os.Stdin variable
• Full module test suite go test ./... — all 29 packages pass
• JSON output uses snake_case keys (import_path, is_variadic, is_generic, etc.) matching core types from PR-01

🤖 Generated with Claude Code

[safedep]

SafeDep Report Summary

No dependency changes detected. Nothing to scan.

_{This report is generated by SafeDep Github App}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.09%. Comparing base (8fe4410) to head (10f5ae8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #548      +/-   ##
==========================================
+ Coverage   82.64%   83.09%   +0.45%     
==========================================
  Files         140      141       +1     
  Lines       17064    17531     +467     
==========================================
+ Hits        14103    14568     +465     
- Misses       2421     2422       +1     
- Partials      540      541       +1     

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[shivasurya]

• feat(go): Replace hardcoded stdlib set with GoImportResolver struct (PR-09) #557
• feat(go): Add stdlib metadata to MCP call graph tool responses (PR-08) #556
• feat(go): Close stdlib type inference gap in GetReturnType (PR-07b) #555
• feat(go): Resolve stdlib return types in variable extraction (PR-07) #554
• feat(go): Wire stdlib loader into builder pipeline (PR-06) #553
• feat(go): Add Go version detection and stdlib loader init (PR-05) #552
• feat(go): Add Go stdlib R2 publishing pipeline (PR-04) #551
• feat(go): Add Go stdlib remote registry loader with lazy caching (PR-03) #549
• feat(go): Add Go stdlib extraction tool for registry generation (PR-02) #548 👈 (View in Graphite)
• feat(go): Add Go stdlib registry data structures and types (PR-01) #546
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[shivasurya]

Merge activity

• Feb 25, 3:17 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Feb 25, 3:19 AM UTC: Graphite rebased this pull request as part of a merge.
• Feb 25, 3:19 AM UTC: @shivasurya merged this pull request with Graphite.

[github-actions]

Code Pathfinder Security Scan

No security issues detected.

Metric	Value
Files Scanned	4
Rules	38

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