[fehmer]

Summary

Adds hideModal to the dev-only window.__mt debug handle, so browser checks can close modals the same way they open them (showModal was already exposed).

 const mt = {
   getConfig,
   setConfig,
   showModal,
+  hideModal,
   restartTest,
   ...
 };

 | `showModal(id)` | open a modal by `ModalId` |
+| `hideModal(id)` | hide a modal by `ModalId` |

The __mt parity test (frontend/__tests__/dev/expose.spec.tsx) enforces the doc table and the handle list the same members in both directions; both sides are updated in this PR.

Evidence

• Before: window.__mt.hideModal was undefined — agent browser checks could open a modal but had no direct way to close it.
  After: pnpm vitest run __tests__/dev/expose.spec.tsx → 1 passed (doc ↔ handle parity, incl. hideModal); oxlint --type-aware --type-check clean. hideModal itself is the existing states/modals.ts setter already consumed by AnimatedModal; only its exposure is new.

Merge Danger

Door: Two-way

Dev-only handle loaded behind import.meta.env.DEV; no production surface. Reverting the commit fully undoes it.

Blast Radius: Dev console

One extra function on the debug object in dev builds; no UI, behaviour or API change.