composer: drop the hardcoded model fallback

Until /v1/settings supplies the list the picker is a disabled "Loading models…" chip.
The baked-in list had gone stale and offered phantom ids during the boot race.

surfaces/gui/e2e/composer-model-loading.spec.ts

@@ -0,0 +1,18 @@
+import { test, expect } from "./fixtures";
+
+// The composer must never advertise models the backend didn't confirm: before the
+// /v1/settings list arrives (cold app boot races the sidecar), the picker is a
+// disabled "Loading models…" chip — NOT a hardcoded fallback list, which went stale
+// and offered phantom ids (caught by owner, 2026-07-21).
+test("picker shows a disabled Loading-models chip until the list arrives", async ({ page }) => {
+  await page.route("**/v1/settings", (r) =>
+    r.fulfill({
+      json: { model: "gpt-5.5", models: [], model_labels: {}, has_key: true, model_ready: true, onboarded: true, nav_layout: "flat" },
+    }),
+  );
+  await page.goto("/");
+  const chip = page.getByTestId("models-loading");
+  await expect(chip).toBeVisible();
+  await expect(chip).toBeDisabled();
+  await expect(chip).toContainText("Loading models…");
+});