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/conversation-list.tsx

@@ -0,0 +1,57 @@
+'use client';
+
+import { cn } from '@/lib/cn';
+import type { Conversation } from '@/lib/types';
+
+interface ConversationListProps {
+  conversations: Conversation[];
+  activeId: string | null;
+  onSelect: (id: string) => void;
+  onNew: () => void;
+}
+
+export function ConversationList({
+  conversations,
+  activeId,
+  onSelect,
+  onNew,
+}: ConversationListProps): React.ReactElement {
+  return (
+    <div className="flex h-full w-64 flex-col border-r border-surface-border bg-surface-card">
+      <div className="flex items-center justify-between p-3">
+        <h2 className="text-sm font-medium text-text-secondary">Conversations</h2>
+        <button
+          type="button"
+          onClick={onNew}
+          className="rounded-md px-2 py-1 text-xs text-blue-400 transition-colors hover:bg-surface-elevated"
+        >
+          + New
+        </button>
+      </div>
+
+      <div className="flex-1 overflow-y-auto">
+        {conversations.length === 0 && (
+          <p className="px-3 py-2 text-xs text-text-muted">No conversations yet</p>
+        )}
+        {conversations.map((conv) => (
+          <button
+            key={conv.id}
+            type="button"
+            onClick={() => onSelect(conv.id)}
+            className={cn(
+              'w-full px-3 py-2 text-left text-sm transition-colors',
+              activeId === conv.id
+                ? 'bg-blue-600/20 text-blue-400'
+                : 'text-text-secondary hover:bg-surface-elevated',
+            )}
+          >
+            <span className="block truncate">{conv.title ?? 'Untitled'}</span>
+            <span className="block text-xs text-text-muted">
+              {new Date(conv.updatedAt).toLocaleDateString()}
+            </span>
+          </button>
+        ))}
+      </div>
+    </div>
+  );
+}