Mic: auto-stop on silence (one-click dictation)

[falkoro]

Dictation was two clicks (start → click again to stop + transcribe). This adds a Web Audio level monitor that auto-finishes once you pause, so it's one click: click Mic → speak → pause → text drops in.

• monitorSilence() taps the mic stream via an AnalyserNode, tracks RMS, and calls the shared finishActiveDictation() after 1.2s of quiet (once speech was heard).
• Manual Mic-to-stop click still works (shared finish path).
• Degrades gracefully: no Web Audio → no-op; a hot/noisy mic that never goes "quiet" just falls back to the manual stop. Safety caps: no-speech 8s, max-take 30s.
• Whisper latency measured at ~0.4s for a short clip, so no persistent server needed — the win is removing the second click + the pause, not raw transcode speed.

Verified in a real browser with a stubbed speak-then-silence stream: one click, auto-finished and transcribed with no second click.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Converts mic dictation from a two-click (start/stop) flow to a one-click flow by adding a Web Audio AnalyserNode-based RMS monitor that auto-finishes recording after a brief pause, while keeping the manual stop click and recorder-error paths intact via a shared finishActiveDictation() function.

Changes:

• Add stopMonitor teardown hook on ActiveDictation and invoke it in both stopDictation() and the new finishActiveDictation() shared finish path.
• Add monitorSilence() which polls RMS every 120 ms and triggers onDone after 1.2 s of silence post-speech, with 8 s no-speech and 30 s max-take safety caps; degrades to a no-op when Web Audio is unavailable.
• Update the recording status copy and wire toggleDictation()'s second-click branch to the shared finish path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
frontend/actions.ts	Adds stopMonitor, finishActiveDictation(), and monitorSilence(); routes manual stop and auto-stop through the shared path; updates status message.
public/actions.js	Compiled JS mirror of the frontend/actions.ts changes.

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