Frontend plumbing for the Photos v2 increase from 4 to 10 images.
- Bump MAX_IMAGES from 4 to 10 in the composer; downstream consumers read the
constant dynamically, so selection limits and copy follow automatically.
- In-feed display rule per the Photos v2 spec: 1 image renders the single
view, 2-4 render the existing grid, >4 render the carousel. This is gated
behind the existing PostGalleryEmbedEnable flag, which now acts as a
carousel kill-switch.
- Fix the reply-to thumbnail to show a 2x2 preview of the first 4 images for
any post with >=4 images (previously it rendered blank for >4).
Note: actually publishing >4 images additionally requires the
app.bsky.embed.images lexicon maxLength to be raised in @atproto/api (PR in
flight). Until that lands, posts with >4 images are rejected by
applyWrites({validate: true}). This change is UI-only and safe behind the flag.
APP-2197
vineyardbovines
843b9b540f