test(mobile): give the shell keyboard bar stub a classList.toggle

A semantic conflict between two PRs that were each green on their own:
#268 added this test with a fake bar element whose classList carries only
add/remove/contains, and #270 added syncReadMyMind() to init(), which
toggles the RMM marker class with an explicit force argument. Neither
branch saw the other, so the failure only appeared once both were on
master. Production is unaffected: init() builds a real element via
document.createElement, which has toggle.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/mobile-shell-keyboard.test.ts

@@ -108,6 +108,14 @@ function fakeBarElement() {
       add: (name: string) => classes.add(name),
       remove: (name: string) => classes.delete(name),
       contains: (name: string) => classes.has(name),
+      // init() calls syncReadMyMind(), which toggles the 🧠 marker class on the
+      // bar with an explicit force argument.
+      toggle: (name: string, force?: boolean) => {
+        const on = force === undefined ? !classes.has(name) : force;
+        if (on) classes.add(name);
+        else classes.delete(name);
+        return on;
+      },
     },
     get innerHTML() {
       return html;