[pratikbuilds]

Message renders an agent, person or own message with an avatar, header, content, footer and send status; own messages sit in a bubble, and markdown comes only through MessageContent's render prop. MessageFold folds a long answer and keeps the reader's place when folding from inside it. MessageActions puts extras in an overflow menu without an optional peer, and MessageReactions, MessageReplies and useCopy cover reactions, reply summaries and copy feedback. A failed message offers a retry.

Stacked on #8: review only this commit. Part of corbitsdev#94.

Notes for review

• Message renders its own send status line (sending; failed with error and Retry) unless a MessageSendStatus is placed among its children; a failure that happens after mount is announced once (polite), never for messages that mount failed, and not inside a role=log (the log announces it). The article is named by MessageHeader's author unless the host labels it.
• MessageFold takes a length (threshold 6000), never folds while streaming, starts open if it mounted while streaming, unfolds when focus moves inside; it starts folded by default, so pass defaultOpen to keep the newest answer open. Place-keeping uses the nearest scroll container, not useConversation.
• Avatar initials come from a local helper (the old chat-message helper is removed at the cutover).
• MessageSendStatus and MessageHeader register through Message's context, so they work at any depth (e.g. inside MessageFooter) and Message never doubles the status line. The live region belongs to Message and reads the current error (or "Not sent."). Server-rendered HTML shows the default line until hydration registers a placed one.

Verification

• This commit passes bun run typecheck and bun run lint on its own (the stack is checked commit by commit).
• At the top of the stack: bun run check, bun run build, bun run dep-guard, bun run contrast-test and bun run test:e2e (Playwright specs and the Storybook axe sweep in light and dark) pass.

Closes corbitsdev#98

[pratikbuilds]

Moved upstream: corbitsdev#121