v0.7.0 — GIF export

New: --gif writes an optimized animated GIF next to the MP4 — narration captions burned in (GIFs are silent), two-pass palette, configurable width/fps. --gif-steps open-modal..create-event excerpts a step range, resolved from the timing manifest (and remapped through --idle-speedup when active). The attached GIF was produced by exactly that command against the example app. Closes #4.