fix(voice): gapless audio chunk playback

[cjol]

This PR fixes audible clicks at audio chunk boundaries during agent speech in VoiceClient. Closes #1736.

Why

• VoiceClient played each response chunk by starting it at currentTime and waiting for its ended event before scheduling the next. The round-trip latency (event-loop delay plus the next chunk's setup) left a few milliseconds of silence at every seam, audible as a periodic click.
• We could have reduced the latency by overlapping decode and schedule, but the fundamental problem is that ended callbacks run on the main thread, not the audio clock, so there will always be some gap.
• Instead, we now schedule chunks back-to-back on the audio clock itself using a playback cursor. Consecutive chunks butt together sample-tight because each starts exactly when the previous ends, regardless of main-thread latency.

Code Changes

• packages/voice/src/voice-client.ts

  • Replaced the single #activeSource with a #scheduledSources set and a #playbackCursor. Each incoming chunk is scheduled at Math.max(currentTime, cursor), and the cursor is advanced by the chunk duration.
  • Playback now counts as active until the last scheduled source finishes, so barge-in detection (user transcript interrupt) keeps working through the scheduled tail.
  • #stopPlayback stops every scheduled source, not just the current one, so an interrupt or end-call cleanly cancels the whole pipeline.
  • Reset the cursor on end-call so a subsequent call starts fresh instead of picking up a stale offset.

• packages/voice/src/tests/voice-client.test.ts

  • Added gapless playback tests: consecutive chunk scheduling, catch-up when the cursor falls behind currentTime, interrupt stops all scheduled chunks, barge-in works through the scheduled tail, and cursor reset on end-call.

---

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🦋 Changeset detected

Latest commit: 8e4717e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@cloudflare/voice	Patch

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