The composer on the index page was rendering whatever avatar was set
in `auth.users.user_metadata.avatar_id` at signup time — never updated
when the user changes their avatar via Profile-Edit (those edits go to
`profiles` table only, JWT claims stay stale).
useMe() is the single source of truth that joins both server-side (see
hooks/useMe.ts:15-18 comment that explicitly lists ComposeCard as a
consumer that should subscribe). Switched the avatar + nickname reads
to useMe(); future PATCH /api/auth/me followed by invalidateMe() now
updates the composer avatar in real time alongside the AppHeader.
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