feat(studio): render geometry-sized video filmstrips

[miguel-heygen]

Summary

Video clips request a geometry-sized filmstrip after measurement and keep a one-frame poster tier available during fast scroll. Geometry requests use stable quantized cache identities and one 4K geometry ceiling.

Before

Origin/main, timeline region at Fit with video clips and the Voiceover audio row at rest:

Origin/main, mid-scroll timeline region with video clips and the Voiceover audio row:

Origin/main, the same timeline at 4x zoom and the same scroll position as After:

After

After the change, timeline region at Fit with video clips and the Voiceover audio row:

After the change, timeline region at 4x zoom with video clips and the Voiceover audio row:

The Footage Frame 1 and Footage Frame 2 no preview labels are not an intended 4x behavior. The non-rich one-frame poster lease remains active at every zoom and is the fallback while rich work is unavailable; those rows are failing both poster and rich decoding in this capture and therefore remain an open preview defect, not an expected filmstrip state.

Decode cost

Devbox decode-cost proxy on the 1080x1920 fixture, evenly spaced timestamps across the first 6 seconds, 3 runs: 6 frames averaged 1.67 s; 20 frames averaged 5.47 s, 3.26x. The 500px example needs 5 visible frames but quantizes the rich request to 8, trading a bounded decode step for stable cache identities. Every video clip now enqueues TWO jobs where main enqueued one, against concurrentVideoDecodes: 2; the 1-frame poster is what paints during scroll, and the filmstrip follows once scrolling settles.

Scheduler safety

120 mounted clips do not decode 20 frames each at once. The scheduler limits video work to the concurrency bucket at packages/studio/src/player/lib/thumbnailScheduler.ts:345-348, pauses only rich work while scrolling at packages/studio/src/player/lib/thumbnailScheduler.ts:207-210 and :258-261, and retains results only within byte and entry budgets at packages/studio/src/player/lib/thumbnailScheduler.ts:327-334 and :384-392, configured by packages/studio/src/player/lib/timelineViewportBudgets.ts:70-82. The one-frame poster request is non-rich, so it remains eligible during scrolling. Quantised request counts and the cache byte budget keep a 120-clip timeline from holding 120 x 20 decoded frames.

Validation

• Focused Studio suites: 26 tests passed for poster deferral, two-tier requests, and thumbnail geometry.
• Studio typecheck passed after generated core artifacts were built; Oxlint and oxfmt passed on the changed files.
• The capture script waited for readiness, asserted a non-zero clip count, and asserted the audio control before taking screenshots.
• The 4K ceiling is Math.ceil(3840 / (66 * (16 / 9))), named once with its geometry reasoning beside the owner budget.