fix: prevent double notification sound playback

[hannesrudolph]

Problem

Notification sounds sometimes play twice, with the second starting milliseconds after the first. This is caused by React <StrictMode> in webview-ui/src/index.tsx which intentionally double-fires effects in development builds. The sound-triggering useDeepCompareEffect in ChatView.tsx has no cleanup function, so StrictMode's mount → cleanup → mount cycle plays the sound twice. Since use-sound (Howler.js) defaults to interrupt: false, both audio instances play concurrently.

Root Cause Analysis

• Systematically investigated and verified against source code across 6 analysis laps
• Eliminated 5 alternative hypotheses (dual messages, multiple panels, partial transitions, Howler reinit, multiple setState)
• Confirmed React StrictMode as the sole mechanism

Fix

Two layers of protection:

1. interrupt: true on all useSound hooks — Tells Howler.js to stop any playing instance before starting a new one, preventing overlapping audio regardless of cause
2. Ref-based debounce on playSound() — Tracks last-played timestamp per audio type, skips calls within 100ms window. Directly neutralizes StrictMode's double-fire

Testing

• Added 2 new tests in ChatView.notification-sound.spec.tsx:
  • "should not play the same sound type twice within 100ms"
  • "should allow playing the same sound type again after 100ms"
• All existing tests pass (30/30)

Files Changed

• webview-ui/src/components/chat/ChatView.tsx
• webview-ui/src/components/chat/__tests__/ChatView.notification-sound.spec.tsx

---

Important

Fix double notification sound playback by setting interrupt: true for useSound hooks and adding a debounce mechanism in ChatView.tsx.

• Behavior:
  • Set interrupt: true for useSound hooks in ChatView.tsx to prevent overlapping audio.
  • Implement ref-based debounce in playSound() to skip sound playback within 100ms window.
• Testing:
  • Added tests in ChatView.notification-sound.spec.tsx to verify sound is not played twice within 100ms and is played after 100ms.
  • Tests ensure no sound is played when there are queued messages or when the message is partial.
• Files Changed:
  • ChatView.tsx
  • ChatView.notification-sound.spec.tsx

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[roomote]

Oroocle   See task

Review complete -- no issues found. The interrupt: true option is valid per use-sound v5 types, the ref-based debounce is correctly keyed per audio type, and both new tests pass alongside the existing 4.

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