⚡ Bolt: Optimize sub-interval extraction to O(log n)

[toreleon]

💡 What: Optimized intervalCloses to extract time-series sub-intervals using an $O(\log n)$ binary search (findLastBarIndex) and .slice(), eliminating the prior $O(n)$ .filter() and $O(n \log n)$ .sort() calls.
🎯 Why: In backtestRunner.ts, extracting sub-intervals from large OHLCV bar arrays is a hot path. The previous implementation iterated over the entire array for every extraction, which scales poorly with large historical datasets, despite the data inherently being sorted by time.
📊 Impact: Reduces time complexity of sub-interval extraction from $O(n \log n)$ to $O(\log n)$, significantly lowering the computational overhead of generating backtest turns across long timelines.
🔬 Measurement: pnpm test and pnpm typecheck pass successfully, and edge cases (where interval boundaries are outside array bounds or do not align perfectly with bars) are correctly covered by bounds checking logic.

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PR created automatically by Jules for task 9599330657436624779 started by @toreleon

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