fix(desktop): persist OpenAI text-only transcripts

[ComputelessComputer]

Synthesize approximate transcript words for batch responses without word timings so OpenAI GPT transcription results are saved and summaries can run.

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Note

Medium Risk
Changes batch transcription persistence behavior by generating synthetic WordLike timing data when providers return transcript text without word-level timings, which could affect downstream alignment/speaker-hint indexing. Scope is localized to batch result handling and covered by a new unit test.

Overview
Batch result handling now supports text-only alternatives: when a BatchResponse includes a transcript but no words, it synthesizes WordLike entries with approximate 400ms durations and persists them instead of dropping the result.

Adds a regression test ensuring handleBatchResponse persists these synthesized words and still clears batch/batchPreview state after persistence.

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Missing wordOffset update for synthesized words path

Medium Severity

When synthesizeWordsFromTranscript produces words for a text-only channel, those words are pushed into allWords but wordOffset is not incremented before returning. If a subsequent channel in the same response has real word timings with speaker hints, the hints' wordIndex values will be computed with a stale wordOffset, causing them to reference incorrect positions in the merged allWords array.

 

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