Behind the new `composer:image_layout_toggle:enable` feature gate, show
a pill button in the composer toolbar (next to the labels button) when a
post has 2-4 images. The button switches the draft between the legacy
`app.bsky.embed.images` shape (grid) and the newer
`app.bsky.embed.gallery` shape (carousel, previously only used for 5+
images). Gallery embeds now always render with the carousel layout so
the choice is reflected for viewers.
The button is wrapped in a one-time tooltip nudge, following the same
pattern as the threadgate button, and emits a
`composer:imageLayout:toggle` metric.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SvDXhHEBCjAfokEFK8pHt8
Claude
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