- useMessages exposes upload(); Thread gains a hover reaction picker (react to
a message) and an attach button (upload → stage → send), plus inline image /
file rendering of message attachments — all capability-degrading (hidden when
the adapter lacks react/upload)
- themeable styles for the picker, attach button, staged chip, and attachments
- 57 tests still green
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
maaz519
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