Module-tier chat composer wrapper — forwards submit events, propagates [disabled], slot vocabulary for future composer surfaces.
Forwards inner submit events as composer-submit, propagates [disabled] to the inner input, slot vocabulary for future composer surfaces (file attach, autocomplete trigger, model picker). JS-bearing.
Typical placement inside <chat-shell>:
Per ADR-0023, the chat cluster's bespoke family — <chat-shell> (host), <chat-thread>, <chat-composer>, <chat-sidebar> (JS-bearing) + <chat-header>, <chat-status>, <chat-empty> (CSS-only). Mirrors the admin cluster's pattern.