test(ai): answer both switch readers from one source in flag mocks

Eight files mocked `@/lib/feature-flags` with `getAssistantFlags` alone.
The capability loader reads `loadAssistantSwitches`, so wherever it ran
it threw and every capability resolved to `check_failed`. A shared
factory now points both readers at the function the test drives.

Only the config-change chain reached the loader. Its fixture means AI
switched off by the operator; it now supplies the loader's other inputs
and asserts `operator_disabled` on the digest, so a starved loader turns
it red instead of passing on the failure path.

src/__tests__/helpers/assistant-switches-mock.ts

@@ -0,0 +1,63 @@
+/**
+ * A `@/lib/feature-flags` mock whose two readers can never disagree.
+ *
+ * The module has two readers of the operator's assistant switches:
+ * `getAssistantFlags()`, which the crons and a few routes read directly, and
+ * `loadAssistantSwitches()`, which the AI capability loader reads. A mock that
+ * stubs only the first leaves the second undefined, the loader throws, and
+ * every capability resolves to `check_failed`. Nothing goes red: a test that
+ * meant "AI on" quietly runs the "AI unavailable" branch instead, and a test
+ * that meant "AI off for reason X" passes for reason `check_failed`.
+ *
+ * So both readers answer from one source. Hand the factory the function the
+ * test already drives (or let it make one), and `loadAssistantSwitches` reads
+ * whatever that function currently returns:
+ *
+ * ```ts
+ * const getAssistantFlags = vi.fn();
+ * vi.mock("@/lib/feature-flags", async () =>
+ *   (await import("@/__tests__/helpers/assistant-switches-mock"))
+ *     .mockAssistantSwitches((...a) => getAssistantFlags(...a)),
+ * );
+ * ```
+ *
+ * `loadAssistantSwitches` is a plain function, not a `vi.fn`, so a
+ * `vi.resetAllMocks()` in the test cannot strip it back to `undefined`.
+ * `src/__tests__/feature-flags-mock-guard.test.ts` refuses a
+ * `vi.mock("@/lib/feature-flags", …)` that provides neither this helper nor
+ * `loadAssistantSwitches` by name.
+ */
+import { vi } from "vitest";
+
+import type { AssistantFlagSet } from "@/lib/feature-flags";
+
+/** Every switch on: what a fresh install reads. */
+export const ALL_SWITCHES_ON: AssistantFlagSet = Object.freeze({
+  enabled: true,
+  coach: true,
+  briefing: true,
+  insightStatus: true,
+  documentAi: true,
+});
+
+/** Every switch off, as an operator who turned the assistant off has it. */
+export const ALL_SWITCHES_OFF: AssistantFlagSet = Object.freeze({
+  enabled: false,
+  coach: false,
+  briefing: false,
+  insightStatus: false,
+  documentAi: false,
+});
+
+type SwitchReader = (...args: never[]) => unknown | Promise<unknown>;
+
+export function mockAssistantSwitches(
+  getAssistantFlags: SwitchReader = vi.fn(async () => ({
+    ...ALL_SWITCHES_ON,
+  })),
+) {
+  return {
+    getAssistantFlags,
+    loadAssistantSwitches: async () => getAssistantFlags(),
+  };
+}