Write transcript to file every 20 s and refresh note summary after each write

[Copilot]

Without periodic saves, a crash or unexpected close during a long recording would lose all transcribed content — the summary was only written to the note on Stop.

Changes

• LIVE_CHUNK_MS 5 000 → 20 000 ms — transcription chunks are now processed and written to the transcript file every 20 seconds.
• Periodic summary refresh — after each successful transcriptAppend, refreshSummaryFromFile() is called immediately (live chunks only), so the note's summary block stays current throughout the recording. A crash or unexpected close now loses at most ~20 s of content.
• Stop path unchanged — the forced final flush (force=true) skips the in-chunk refresh; handleRecordingStop calls refreshSummaryFromFile() explicitly once the complete transcript is on disk.

// transcribeLiveChunk — inner try/catch after Whisper returns text
try {
  await window.electronAPI.transcriptAppend(text);
  if (!force) await refreshSummaryFromFile(); // read-back summarise after confirmed write
} catch (e) {
  console.error('Appending to transcript file failed:', e);
}

The ordering guarantees the file is fully written before it is read back for summarisation, matching the intended contract.

[deanhume]

Not merging this change