fix(frontend): type pushState mocks with real History.pushState signature

- npm run typecheck failed on the 0-arg vi.fn<() => void>() because
  mock.calls[0] became an empty tuple, so calls[0][2] (the URL arg)
  was typed as undefined.
- Constrain the mock to the real (state, unused, url?) signature so
  mock.calls[0] is a 3-tuple and [2] is string-or-URL-or-null. Drops
  the as-string cast at every callsite.

src/hooks/useDrawerUrlState.test.ts

@@ -58,11 +58,13 @@ function setLocation(url: string): void {
 describe("useDrawerUrlState", () => {
   // `vi.fn()` with no args in vitest 4 is typed `Mock<Procedure |
   // Constructable>`, which carries a constructor signature and won't
-  // assign to `() => void`. Constraining the generic to `vi.fn<() => void>()`
-  // gives a plain function-typed mock that flows directly into `pushState`
-  // / `replaceState` slots.
-  let pushStateMock: ReturnType<typeof vi.fn<() => void>>;
-  let replaceStateMock: ReturnType<typeof vi.fn<() => void>>;
+  // assign to a real `pushState` slot. Constrain the generic to the
+  // `History.pushState` signature so the mock flows into `vi.stubGlobal`
+  // without complaint AND `mock.calls[0]` is typed as a 3-tuple, letting
+  // us read `calls[0][2]` (the URL) without an `as unknown` cast.
+  type PushState = (state: unknown, unused: string, url?: string | URL | null) => void;
+  let pushStateMock: ReturnType<typeof vi.fn<PushState>>;
+  let replaceStateMock: ReturnType<typeof vi.fn<PushState>>;
 
   beforeEach(() => {
     pushStateMock = vi.fn();