polish: compact composer variant for the editor Create tab

[thisiscsim]

Summary

• Matches the editor panel composer to Figma node 346:10331: a variant="compact" on Composer renders a single white card (no gray footer shell) with just the mode + effort pills.
• Aspect ratio, duration, and the reference-apply mode fold into a new slider-icon settings popover on the right of the toolbar (icon harvested from the frame as settings-slider).
• The reference footer strip is dropped in compact — references live in the panel's References tab; the zero-state home keeps the wide variant unchanged. Critique-mode benchmark dropzone still works in both.
• Aspect/duration/reference-mode menu sections are extracted once and shared between the wide pills and the compact popover.

Test plan

• npm run typecheck && npm test && npm run build green (146 tests)
• Editor Create tab: composer shows Generation + Ultra pills, slider popover contains Aspect ratio / Duration / Apply references
• Zero-state home composer unchanged (all pills + Add reference footer)
• Critique mode in the editor still shows the benchmark dropzone

Renderer-only change — HMR covers it, no dev restart needed.

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