fix(spec): drop hardware back from defaultActions to stay in-app

pkg/spec/src/defaults/actions.ts

@@ -1,14 +1,15 @@
-import { pressKey, swipes, taps, typing, weighted } from "../actions.ts";
+import { swipes, taps, typing, weighted } from "../actions.ts";
 import type { ActionGenerator } from "../types.ts";
 
 export { pressKey, swipes, taps, typing, waitOnce } from "../actions.ts";
 
 // A broad exploration generator: tap things, type edge-case values into fields,
-// swipe, and occasionally press back. Layer it under targeted depth flows so the
+// and swipe. Layer it under targeted depth flows so the fuzzer wanders the whole
-// fuzzer wanders the whole app while still driving the paths an author wrote.
+// app while still driving the paths an author wrote. It deliberately omits the
+// hardware back key: backing out past the app's root screen exits the app under
+// test, and exploration must stay within the app.
 export const defaultActions: ActionGenerator = weighted(
-  [50, taps],
+  [55, taps],
   [30, typing],
-  [10, swipes],
+  [15, swipes],
-  [10, pressKey],
 );