feat: chat reactions

components/chat/chat-composer.tsx

@@ -37,6 +37,7 @@ export function ChatComposer({
   replyTo,
   onCancelReply,
   onSend,
+  onTyping,
   conversationId,
   disabled = false,
   placeholder = "Message…",
@@ -45,6 +46,8 @@ export function ChatComposer({
   conversationId: string;
   replyTo: ChatMessage | null;
   onCancelReply: () => void;
+  /** Called on each keystroke; throttled by the caller. */
+  onTyping?: () => void;
   onSend: (
     body: string,
     replyToId?: string,
@@ -257,7 +260,13 @@ export function ChatComposer({
           value={value}
           disabled={disabled}
           placeholder={placeholder}
-          onChange={(e) => setValue(e.target.value)}
+          onChange={(e) => {
+            setValue(e.target.value);
+            // Fired on every keystroke; the handler throttles itself, so the
+            // thread hears "still typing" every few seconds rather than per
+            // character.
+            onTyping?.();
+          }}
           onKeyDown={(e) => {
             // Enter sends on a physical keyboard; Shift+Enter makes a newline.
             // On touch keyboards Enter must insert a newline instead — there is