⚡ Bolt: Optimize diffTests string processing bottleneck

[google-labs-jules]

💡 What:
Optimized the diffTests function in both cli/commands/diff.mjs and cli/validators/docs-diff.mjs. The logic previously utilized multiple nested .filter() and .some() loops that repeatedly calculated basename() on identical strings and iterated over arrays excessively. The updated code pre-computes base paths into objects, uses a single cross-check nested loop, and relies on Sets to track matches instantly.

🎯 Why:
To remove the O(N * M) string manipulation overhead and multi-pass traversal overhead. In large repositories with thousands of documented and actual test files, repeatedly doing basename() inside an inner nested loop mapping causes major CPU slowdowns.

📊 Impact:
Drastically cuts down array iterations and string operations, particularly basename() processing, transforming multi-pass filtering into a single loop using O(1) Set checks. This results in much faster test file diffing for large test suites.

🔬 Measurement:
Run docguard diff or docguard guard on a codebase with a large number of test files, and observe the overall performance boost and shorter command execution time for the test documentation validation stage.

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PR created automatically by Jules for task 5793606387510942144 started by @raccioly

[google-labs-jules]

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