feat: build the chat + preview + approve interface

- web: two-pane app chrome (chat panel + browser-framed preview)
- ChatPanel, Preview, ApproveBar components + useChat (mock agent for now)
- Fluent/Figma design system (Inter, dark chrome, elevation, motion)
- 107 unit tests + Playwright e2e green; web typechecks + builds

web/src/components/ApproveBar.tsx

@@ -0,0 +1,21 @@
+type ApproveBarProps = {
+  visible: boolean;
+  onApprove: () => void;
+  onReject: () => void;
+};
+
+export function ApproveBar({ visible, onApprove, onReject }: ApproveBarProps) {
+  if (!visible) return null;
+
+  return (
+    <div className="approve-bar">
+      <span className="approve-copy">Looks good?</span>
+      <button className="wursor-approve-button" type="button" onClick={onApprove}>
+        Looks good → Apply
+      </button>
+      <button className="wursor-reject-button" type="button" onClick={onReject}>
+        Not right → Reject
+      </button>
+    </div>
+  );
+}