ML Intern launch card on the HuggingChat home screen (#2566)
Pete is launching ML Intern mode and asked for a CTA on HuggingChat.
This adds a compact card under the home-screen logo whose CTA switches
the mode on (the composer pill then takes over), a "Now with ML Intern!"
label on the welcome modal, and makes the pill open its first-run
onboarding whenever the mode first goes on, not only from its own click.
Dismissal lives in localStorage since the card is a temporary launch
aid; it also retires once the user has a mode conversation, while the
recorder replaces the composer, and on short viewports. The
announcement toast hides while the card shows.
Also fixes the composer's pill row on mobile: reserve room for the mic
and send buttons that are actually present, and keep pills from
shrinking so the MCP favicons are not squashed.
