⚡ Bolt: [performance improvement] Avoid array allocations in buildCandidate

[toreleon]

💡 What: Refactored buildCandidate and rsi14 in src/tools/discover.ts to iterate directly over the source array instead of allocating intermediate arrays.
🎯 Why: Creating arrays with .map() and .slice() inside a tight, concurrent mapping operation creates memory pressure and unnecessary GC pauses.
📊 Impact: Expected to reduce memory allocations and slightly lower GC overhead when processing market data across multiple candidates concurrently.
🔬 Measurement: Verify using memory profiling, and check tests (pnpm test) to ensure output arrays and functionality matches identically.

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PR created automatically by Jules for task 3196409582248946147 started by @toreleon

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