test(webview): pin the other half of the setState fixture's dependency

The previous commit asserted the doc-identity premise but left its twin in
prose: this fixture kills the dispatch-interception mutant only because
setState does not dispatch. If that ever changed, the state would still be
replaced, the test would still pass, and the mutant would quietly survive —
the same silent revival the doc premise had, in the other direction.

A dispatch counter around the call pins it. Measured: making the fixture
dispatch before setState reds the test, and the doc-comparison mutant still
reds it too, so neither pin displaced the other.

Author: mtskf

test/webview/helpers/unstarved-frontier.test.ts

@@ -350,7 +350,18 @@ describe("a state replacement after the LAST gate is refused", () => {
           // Asserted inside the fixture rather than as its own `it`, because a separate
           // test would not be coupled to the state this one actually passes to setState.
           expect(replacement.doc).toBe(view.state.doc);
+          // The other half of the same dependency: this fixture only kills the
+          // dispatch-interception mutant because setState does NOT dispatch. If that ever
+          // changed, the state would still be replaced, this test would still pass, and
+          // that mutant would quietly survive again.
+          let dispatches = 0;
+          const realDispatch = view.dispatch.bind(view);
+          view.dispatch = ((...args: Parameters<typeof realDispatch>) => {
+            dispatches++;
+            return realDispatch(...args);
+          }) as typeof view.dispatch;
           view.setState(replacement);
+          expect(dispatches).toBe(0);
         },
       })
     ).toThrow(