code health improvement: document false positive unused import

[ysdede]

What: Analyzed a reported "unused import" code health issue on line 2 of src/lib/transcription/UtteranceBasedMerger.regression.test.ts.
Why: To prevent the removal of a valid import and maintain type safety. Both UtteranceBasedMerger and type ASRWord are actively used in the file; specifically, ASRWord is utilized as the explicit return type for the wordsFromTuples function.
Verification: Attempted compiling the file with unused locals warnings (tsc --noUnusedLocals) and executed the test suite (bun test src). Ensured that no code modification was made as both imports are actively required.
Result: Concluded that the reported issue is a false positive. Preserved the codebase's type safety and functionality.

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PR created automatically by Jules for task 2514237044911286497 started by @ysdede

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