Build a chat UI

• A scrollable message list with sent and received bubbles, sender names or avatars and a readable timestamp per message (grouped when close in time)
• Sending (Enter, with Shift+Enter for a newline) appends the message immediately in a "sending" state, and a mock server acknowledges it, changing it to "sent" or "failed" with a retry button
• Auto-scroll to the bottom for new messages only if the user was already at the bottom; otherwise show a "New messages" button
• A mock socket delivers incoming messages and "typing..." events; the typing indicator appears and disappears after a short idle timeout
• Empty or whitespace-only messages cannot be sent, and the textarea grows with its content up to a limit
• The socket subscription is created on mount and removed on unmount, and the list is exposed with role="log" and aria-live="polite"

Only after every requirement works.

• Load older messages when scrolling to the top while keeping the scroll position
• Read receipts and message reactions
• Reconnect with exponential backoff and queued unsent messages