⚡ Bolt: [performance improvement] O(1) early exit for confidence level

[seonghobae]

💡 What: Replaced the unconditional Array.prototype.reduce() array scan in ConfidenceMetric with a for...of loop containing an early exit condition when encountering the absolute bound ("low").

🎯 Why: To improve UI render times when loading large sets of sections and evaluating rehearsal confidence scores. Using .reduce() executes a full O(N) array scan every time, even if the "lowest" possible bound is the very first element. Breaking out early converts the worst-case O(N) iteration into an O(K) best-case execution, saving CPU cycles when determining confidence badges.

📊 Impact: Reduces unneeded loop iterations to evaluate the summary confidence. O(N) changes to O(K) with short-circuiting.

🔬 Measurement: Verify via npm run test --workspace=apps/desktop to ensure the new short-circuit logic preserves correctness and the added tests pass with 100% coverage.

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PR created automatically by Jules for task 10540046786010334403 started by @seonghobae

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