Fix karaoke highlight crash when editing the transcript

[maboa]

Summary

When the user deletes spans in the transcript while playback is running, hyperaudio-lite's cached wordArr still references the now-detached nodes. If its setTimeout poll fires before the editor's debounced refreshHyperaudioInstance rebuilds the array, updateTranscriptVisualState dereferences word.n.parentNode.classList on a node whose parentNode is null — the rejection happens inside the setTimeout callback so the polling chain dies silently, freezing the karaoke highlight for the rest of the session.

Monkeypatches updateTranscriptVisualState on the HyperaudioLite instance to filter wordArr to live entries before delegating to the original. The library only uses wordArr via a fresh binary search per call, so a temporarily shrunken array is consistent. The next debounced refreshHyperaudioInstance rebuilds wordArr fully from the live DOM.

Kept the fix in the editor rather than upstream because the race only exists for editor-style consumers that mutate the transcript DOM at runtime; hyperaudio-lite is otherwise read-only.

Fixes #294.

Test plan

• Play the demo media. Rapidly delete words/paragraphs from the transcript. Confirm no console errors and the highlight keeps tracking the audio.
• Strikethrough toggle + gap-skip continue to work as before.
• Switch to caption mode and back via restoreTranscript — confirm the patch is applied to the fresh HyperaudioLite instance (re-applied on every hyperaudio() call).
• Page load with no edits → highlight behavior unchanged from main.