⚡ Bolt: [performance improvement] Optimize string conversions in checkUntrackedTodos

[raccioly]

💡 What:

• Moved content.toLowerCase() into loadTrackingDocs to precompute the lowercased content once per file.
• Hoisted todo.text.toLowerCase().trim() and string substring operations outside of the trackingContent.some() loop inside checkUntrackedTodos.

🎯 Why:
Inside checkUntrackedTodos, doc.content.toLowerCase() was repeatedly executed in the nested inner loop against every file, for every TODO item. Furthermore, todo.text.toLowerCase().trim() was also redundantly recalculated for every document. For codebases with many TODOs and large tracking docs, this formed a noticeable O(N*M) string allocation and parsing bottleneck.

📊 Impact:
Reduces redundant string lowercasing and trimming operations from (Todos * Docs) + (Todos * Docs) to Todos + Docs, significantly reducing memory allocation and improving the validator run time for large repositories.

🔬 Measurement:
Run the CLI suite or manually execute node cli/validators/todo-tracking.mjs (indirectly via guard). The unit tests still pass via pnpm test.

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PR created automatically by Jules for task 17971078274132913942 started by @raccioly

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