feat(web): chat UI with conversations and WebSocket streaming (#84)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/chat/streaming-message.tsx

@@ -0,0 +1,22 @@
+'use client';
+
+/** Renders an in-progress assistant message from streaming text. */
+interface StreamingMessageProps {
+  text: string;
+}
+
+export function StreamingMessage({ text }: StreamingMessageProps): React.ReactElement | null {
+  if (!text) return null;
+
+  return (
+    <div className="flex justify-start">
+      <div className="max-w-[75%] rounded-xl border border-surface-border bg-surface-elevated px-4 py-3 text-sm text-text-primary">
+        <div className="whitespace-pre-wrap break-words">{text}</div>
+        <div className="mt-1 flex items-center gap-1 text-xs text-text-muted">
+          <span className="inline-block h-2 w-2 animate-pulse rounded-full bg-blue-500" />
+          Thinking...
+        </div>
+      </div>
+    </div>
+  );
+}