[LeanBitLab]

💡 What: Replaced text.lowercase().split(NON_LETTER_REGEX).filter { it.length >= 2 } in LanguageDetector.detectByHeuristics with a manual character iteration loop using a StringBuilder.

🎯 Why: Calling .split(Regex) and chained .filter created unnecessary intermediate list allocations and involved regex engine execution overhead during text classification and proofreading hot paths, causing unnecessary GC pressure.

📊 Expected Impact: Reduced GC pressure and faster execution in text processing hot paths by avoiding regex compilation/execution and eliminating intermediate object allocations.

🔬 Verification: Verified locally via ./gradlew :app:assembleStandardDebug and ./gradlew :app:testStandardDebugUnitTest. Tests completed successfully.

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PR created automatically by Jules for task 5320803216098800702 started by @LeanBitLab

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[LeanBitLab]

Merged into main via commit 21622d7.