Step 1 full re-run @ 15fps with compound+fallback prompts and containment merge (55 clips)

Re-export 21 clips: scene.json objects/[] now populated from sam3_obj_data when no SAM3D mesh; silver-can clip uses 'silver can' instead of 'can of olives' (SAM3 hits 4/4 vs 3/4)

Replace samples/ with 21-clip Step 1 test batch (no SAM3D, no 6DoF)

Refresh dataset: 48 trim-reviewed clips, manual SAM3 prompts, full descriptions in scene.json