feat(studio): add timeline pinch zoom

[miguel-heygen]

Problem

The Studio timeline still only supported button-based zoom, and the ruler stayed too sparse at high zoom levels. Trackpad pinch gestures could also leak into browser/page zoom on macOS.

What this fixes

• Adds trackpad pinch / Ctrl-wheel timeline zoom that preserves the time under the pointer.
• Captures pinch wheel events with a non-passive native listener so browser zoom does not take over.
• Adapts ruler major/minor tick spacing from the current pixels-per-second, so zoomed timelines show denser professional-editor-style timecode labels instead of sparse duration-only labels.

Root cause

Timeline zoom state was only changed by the Fit / plus / minus controls. The ruler tick generator only considered total duration, so the same labels were used regardless of the visible scale. React wheel handling was also too late/passive for preventing browser zoom reliably on macOS pinch events.

Verification

Local

• bun run --filter @hyperframes/studio test src/player/components/Timeline.test.ts src/player/components/timelineZoom.test.ts
• bunx oxlint packages/studio/src/player/components/Timeline.tsx packages/studio/src/player/components/Timeline.test.ts packages/studio/src/player/components/timelineZoom.ts packages/studio/src/player/components/timelineZoom.test.ts
• bunx oxfmt --check packages/studio/src/player/components/Timeline.tsx packages/studio/src/player/components/Timeline.test.ts packages/studio/src/player/components/timelineZoom.ts packages/studio/src/player/components/timelineZoom.test.ts
• bun run --filter @hyperframes/studio typecheck

Browser

• Previewed hf-designer-talk in Studio at http://localhost:5190/?project=hf-designer-talk&record=1#project/hf-designer-talk.
• Verified synthetic pinch wheel events on the timeline were defaultPrevented: true, kept visualViewport.scale at 1, and changed timeline zoom from 100% to 232%.
• Verified the zoomed ruler at 476% displayed denser labels (0:00, 0:10, 0:20, 0:30, …) rather than only sparse 30-second marks.
• Screenshot: /tmp/hf-timeline-proof/hf-designer-talk-ruler-zoom.png

Notes

Stacked on #540 so the GSAP clip stability fix can land independently from the timeline gesture/ruler UX work.

[vanceingalls]

Staff review: approved.

The implementation is scoped well: pinch/Ctrl-wheel handling is attached directly to the timeline scroll container with a non-passive native listener, so it can reliably suppress browser zoom without broadening keyboard or page-level behavior. The zoom-anchor helper is testable and preserves the time under the pointer, and the existing fit/manual scroll reset path still keeps fit mode deterministic.

The ruler changes also look reasonable. Tick spacing now keys off pixels-per-second when available, falls back to duration-based spacing otherwise, and keeps a safety cap to avoid runaway DOM generation. The added tests cover the important zoom-density and subsecond label behavior.

I did not find any blocking issues in this patch.