⚡ Bolt: [performance improvement] Optimize todo tracking validation

[raccioly]

💡 What:
Optimized the validateTodoTracking validator (checkUntrackedTodos) by precomputing expensive string conversions (.toLowerCase()). The .toLowerCase() operation for document content is now done once per document during file loading in loadTrackingDocs. The .toLowerCase() and .trim() operations for TODO items are now hoisted out of the trackingContent.some inner loop.

🎯 Why:
To prevent an O(NM) performance bottleneck in nested loops. Previously, for N TODOs and M tracking documents, the code was executing content.toLowerCase() and todo.text.toLowerCase().trim() NM times on every invocation of docguard guard. By precomputing these, we reduce string processing overhead significantly, making the CLI faster.

📊 Impact:
Significantly reduces string operations from O(N*M) to O(N + M) allocations during the untracked TODOs scan. This improves performance, particularly in codebases with many TODOs and large tracking documents.

🔬 Measurement:
Run pnpm test to verify that functionality remains exactly identical, with the only change being reduced execution time for docguard guard. Test suites run slightly faster due to the reduced string computation overhead.

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PR created automatically by Jules for task 13348412265487393214 started by @raccioly

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