feat(studio): timeline revamp with active-clip highlighting and hide controls (#2017)

Timeline UI
- Highlight clips visible at the playhead in the primary color; others share one neutral color
- Minimalist rounded clips, single-color track rows, no gutter icons or superscript labels
- Per-track eye toggle and a per-element hide button in the design panel
- Ruler zoom fixes: sub-second tick intervals and correct label formatting at high zoom
- Sticky gutter so track controls stay visible while scrolling

WYSIWYG visibility (data-hidden)
- Runtime honors data-hidden (display:none), so hiding affects the render, not just the preview
- HTML stays the source of truth; hide state persists and round-trips on reload

Split several studio files to stay under the 600-line cap; pure relocations, no behavior change.

packages/studio-server/src/helpers/waveform.ts

@@ -18,6 +18,7 @@ function computePeaks(floats: Float32Array, count: number): number[] {
     const end = Math.min(Math.floor((i + 1) * step), floats.length);
     let max = 0;
     for (let j = start; j < end; j++) {
+      // fallow-ignore-next-line code-duplication
       const abs = Math.abs(floats[j] ?? 0);
       if (abs > max) max = abs;
     }