feat(app): checkout diff pane styling and e2e test support

- Style diff file cards edge-to-edge with single divider between files
- Remove monospace font from filenames for better readability
- Add checkout-ship e2e test for app
- Export Page type from e2e fixtures
- Add checkout query hooks for diff, status, and PR status

packages/app/src/hooks/use-checkout-status-query.ts

@@ -0,0 +1,47 @@
+import { useQuery } from "@tanstack/react-query";
+import { useSessionStore } from "@/stores/session-store";
+import type { CheckoutStatusResponse } from "@server/shared/messages";
+
+const CHECKOUT_STATUS_STALE_TIME = 15_000;
+
+function checkoutStatusQueryKey(serverId: string, agentId: string) {
+  return ["checkoutStatus", serverId, agentId] as const;
+}
+
+interface UseCheckoutStatusQueryOptions {
+  serverId: string;
+  agentId: string;
+}
+
+export type CheckoutStatusPayload = CheckoutStatusResponse["payload"];
+
+export function useCheckoutStatusQuery({ serverId, agentId }: UseCheckoutStatusQueryOptions) {
+  const client = useSessionStore(
+    (state) => state.sessions[serverId]?.client ?? null
+  );
+  const isConnected = useSessionStore(
+    (state) => state.sessions[serverId]?.connection.isConnected ?? false
+  );
+
+  const query = useQuery({
+    queryKey: checkoutStatusQueryKey(serverId, agentId),
+    queryFn: async () => {
+      if (!client) {
+        throw new Error("Daemon client not available");
+      }
+      return await client.getCheckoutStatus(agentId);
+    },
+    enabled: !!client && isConnected && !!agentId,
+    staleTime: CHECKOUT_STATUS_STALE_TIME,
+    refetchInterval: 10_000,
+  });
+
+  return {
+    status: query.data ?? null,
+    isLoading: query.isLoading,
+    isFetching: query.isFetching,
+    isError: query.isError,
+    error: query.error,
+    refresh: query.refetch,
+  };
+}