fix: restore transcription word highlighting during audio playback

Re-wire highlightCurrentSection() and clearHighlighting() which became
dead code when the HTML5 audio element was replaced with the Rust cpal
engine. The visualizer loop now highlights the active transcription
section each frame, and pause/ended clear the highlight.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: JSKitty

src/js/voice.js

@@ -1529,6 +1529,10 @@ function handleAudioAttachment(cAttachment, pMessage, msg) {
 
         currentTimeEl.textContent = formatTime(posMs / 1000);
 
+        // Highlight active transcription section if visible
+        const tContainer = audioContainer.querySelector('.transcription-result:not(.hidden)');
+        if (tContainer) highlightCurrentSection(tContainer, posMs);
+
         if (posMs >= durationMs) return; // Let ended event handle cleanup
 
         animationId = requestAnimationFrame(updateVisualizerFromData);
@@ -1674,6 +1678,10 @@ function handleAudioAttachment(cAttachment, pMessage, msg) {
             animationId = null;
         }
 
+        // Clear transcription highlighting
+        const tContainer = audioContainer.querySelector('.transcription-result');
+        if (tContainer) clearHighlighting(tContainer);
+
         // Smoothly wind down bars to paused state
         if (durationMs > 0) {
             const pausedPos = Math.min(playStartPos + (performance.now() - playStartTime), durationMs);
@@ -1811,6 +1819,10 @@ function handleAudioAttachment(cAttachment, pMessage, msg) {
         customPlayer.classList.remove('playing');
         currentTimeEl.textContent = '0:00';
 
+        // Clear transcription highlighting
+        const tContainer = audioContainer.querySelector('.transcription-result');
+        if (tContainer) clearHighlighting(tContainer);
+
         if (animationId) {
             cancelAnimationFrame(animationId);
             animationId = null;