fix: refactor TranscriptionDisplay and fix buffer safety in App.tsx

[ysdede]

This PR addresses two issues:

1. Performance/Stability in UI: TranscriptionDisplay was using MutationObserver to trigger auto-scroll. This has been replaced with a SolidJS createEffect on confirmedText and pendingText props, which is more efficient and idiomatic. The requestAnimationFrame throttling for the actual scroll action is preserved.
2. Critical Bug in Audio Pipeline: In App.tsx, the audio chunk buffer was being transferred to the TenVADWorker via processTransfer. This detached the buffer from the main thread, causing AudioEngine (which owns the buffer and uses it for visualization and ring-buffer writing) to potentially access an invalid/empty buffer. The call was changed to process, which internally copies the buffer before transferring the copy, ensuring the original buffer remains valid for AudioEngine.

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PR created automatically by Jules for task 3897330223291647915 started by @ysdede

[kiloconnect]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• src/App.tsx - TEN-VAD buffer handling fix
• src/components/TranscriptionDisplay.tsx - Auto-scroll refactor

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Changes Overview:

1. App.tsx: Changed from processTransfer() to process() for TEN-VAD worker to preserve the original audio buffer for AudioEngine visualization/ring-buffer usage. The new comment clearly explains the rationale.

2. TranscriptionDisplay.tsx: Refactored from MutationObserver-based auto-scroll to SolidJS createEffect. This is a cleaner approach that automatically tracks dependencies and doesn't require manual cleanup (SolidJS handles effect disposal on component unmount).

Both changes appear to be valid improvements with no security vulnerabilities, runtime errors, or logic issues detected.

[ysdede]

FYI: PR #143 includes related transcript/UI performance containment changes (batched v4 updates + merged-view recompute gating) and links this PR as related context.

[ysdede]

Superseded by PR #134 which includes optimal scrolling dependencies.