fix: call graph correctness and performance improvements

[bubunyo]

Fixes five issues found during evaluation:

• funcKey collision — methods with the same name on different receiver types in the same package collided to the same key. Now uses fn.String() which is receiver-aware and unique.
• Exclude patterns — cfg.Exclude.Patterns and SkipVendor were parsed but never applied. Functions from matched files are now removed from the graph, nodes, reverse index, and owner map.
• Baseline version check — LoadBaseline now rejects baselines whose version doesn't match CurrentVersion, preventing silent wrong diffs from stale snapshots.
• findSSAFunc O(N²) → O(1) — replaced linear CHA node scan with a ssaIndex map built once in BuildGraph().
• isService() O(N) → O(1) — replaced per-call owner scan with a serviceSet precomputed in NewAnalyzer().
• Dead code removed — SourceFileInfo and ImpactIndex in types.go were unused.
  All changes include tests. Full suite passes.

[Copilot]

Pull request overview

This PR addresses five correctness and performance bugs in the buildgraph call graph analyzer:

• funcKey collision fix — funcKey() now uses fn.String() (which includes the receiver type) instead of pkg.path + "." + fn.Name(), preventing name collisions between methods on different receiver types within the same package.
• Exclude patterns enforcement — applyExcludeFilters() is introduced to actually apply cfg.Exclude.Patterns and SkipVendor after BuildGraph(), removing matched functions from all graph structures.
• Baseline version check — LoadBaseline now rejects baselines whose Version does not match CurrentVersion, preventing silent incorrect diffs from stale snapshots.
• O(N²) → O(1) findSSAFunc — A ssaIndex map is built once in BuildGraph() so findSSAFunc is a constant-time lookup.
• O(N) → O(1) isService — A serviceSet is precomputed in NewAnalyzer() for O(1) service membership checks.
• Dead code removed: SourceFileInfo and ImpactIndex types from types.go.

Changes:

• funcKey bug fix, ssaIndex for O(1) lookups, and applyExcludeFilters implementation
• serviceSet precomputation in impact.Analyzer
• CurrentVersion constant and version check in LoadBaseline

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/analyzer/analyzer.go	Core changes: funcKey uses fn.String(), builds ssaIndex in BuildGraph(), adds applyExcludeFilters() and fileMatchesExclude()
pkg/analyzer/analyzer_test.go	Tests for funcKey collision fix and exclude patterns
pkg/analyzer/ssa_index_test.go	Tests for ssaIndex O(1) lookup (internal package test)
pkg/impact/impact.go	serviceSet precomputed in NewAnalyzer(), isService() simplified to O(1) map lookup
pkg/impact/impact_test.go	Tests for serviceSet precomputation
pkg/storage/storage.go	Adds CurrentVersion = "1.0" constant; LoadBaseline now validates version
pkg/storage/storage_test.go	Tests for version validation in LoadBaseline
pkg/types/types.go	Removes unused SourceFileInfo and ImpactIndex types
testproject/core/collision/collision.go	New test fixture with (*A).Run and (*B).Run for collision testing
testproject/services/service-a/main.go	Updated to call both collision methods to exercise the call graph

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

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