[kaffeindecaf]

Summary

• Make progressive content-aware seam scaling the default collapse mode.
• Ramp seam-carved displacement linearly from the source image to the configured target over clip duration, while remapping each frame to the original dimensions.
• Keep the seeded elastic warp selectable as mode=elastic; document controls and update the roadmap.

Verification

• Full test suite passes with optional processors installed.
• Collapse, menu, and layout tests pass; 120-frame mode/size benchmark recorded in scratch.
• Rendered the supplied 2560x1440 clip: source/output mean RGB difference grew from 0.94 at start to 17.42 mid-clip and 23.04 near the end; output retained 377 frames and AAC audio.