perf(runner): confirm focus only when another element holds it

Measured over 717 InputText steps: nothing was focused before the tap 23.8
percent of the time, the target already held focus 60.4 percent, and a
different element held it 15.8 percent. Silent corruption is only reachable
from that third class, and all four real rejections observed came from it.

Gating there keeps every rejection, skips 84.2 percent of the extra hierarchy
reads, and recovers about 8 percent of Android run time. The pre-tap and
post-tap conditions are now the same predicate stated once.

Claude-Session: https://claude.ai/code/session_01A5KmftdEJ49A9z5mF5ESrX

internal/runner/runner_test.go

@@ -910,6 +910,70 @@ func TestApplyAction_InputTextSkipsFocusCheckWhenHierarchyOmitsFocus(t *testing.
 	}
 }
 
+const loginFocusOnNothing = `{"attributes":{"resource-id":"root","bounds":"[0,0,1080,2340]"},"children":[
+	{"attributes":{"resource-id":"LoginEmail","bounds":"[94,240,986,372]"},"focused":false,"children":[]},
+	{"attributes":{"resource-id":"LoginPassword","bounds":"[94,461,986,593]"},"focused":false,"children":[]}
+]}`
+
+// Typed text can only be corrupted into a field that already holds focus, so
+// a pre-tap hierarchy showing focus elsewhere is the one class worth the
+// confirming read.
+func TestApplyAction_InputTextConfirmsFocusWhenAnotherFieldHeldItBeforeTheTap(t *testing.T) {
+	fastFocusSettle(t)
+	tree, err := hierarchy.Parse(loginFocusOnEmail)
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	driverMock := mockdriver.New()
+	driverMock.HierarchyJSON = loginFocusOnPassword
+	action := verifier.Action{
+		Kind: verifier.ActionKindInputText,
+		On:   "id:LoginPassword",
+		Text: "ledger123",
+	}
+
+	mustDispatch(t, driverMock, action, tree)
+	if !containsAction(driverMock.Actions(), mockdriver.ActionHierarchy, "") {
+		t.Errorf("another field held focus before the tap: expected the confirming read, got %v", driverMock.Actions())
+	}
+	if !typedText(driverMock.Actions(), "ledger123") {
+		t.Errorf("expected InputText once the target took focus, got %v", driverMock.Actions())
+	}
+}
+
+// The confirming read is a device round-trip on every InputText step. Where no
+// other element holds focus before the tap there is no field for the text to
+// be corrupted into, so the read buys nothing and must not be paid for.
+func TestApplyAction_InputTextSkipsFocusCheckWhenNoOtherFieldHoldsFocus(t *testing.T) {
+	fastFocusSettle(t)
+	for name, beforeTap := range map[string]string{
+		"target already holds focus": loginFocusOnPassword,
+		"nothing holds focus":        loginFocusOnNothing,
+	} {
+		t.Run(name, func(t *testing.T) {
+			tree, err := hierarchy.Parse(beforeTap)
+			if err != nil {
+				t.Fatalf("Parse: %v", err)
+			}
+			driverMock := mockdriver.New()
+			driverMock.HierarchyJSON = loginFocusOnEmail
+			action := verifier.Action{
+				Kind: verifier.ActionKindInputText,
+				On:   "id:LoginPassword",
+				Text: "ledger123",
+			}
+
+			mustDispatch(t, driverMock, action, tree)
+			if containsAction(driverMock.Actions(), mockdriver.ActionHierarchy, "") {
+				t.Errorf("no other field held focus: expected no confirming read, got %v", driverMock.Actions())
+			}
+			if !typedText(driverMock.Actions(), "ledger123") {
+				t.Errorf("expected InputText, got %v", driverMock.Actions())
+			}
+		})
+	}
+}
+
 func typedText(actions []mockdriver.Action, text string) bool {
 	for _, action := range actions {
 		if action.Kind == mockdriver.ActionInputText && action.Text == text {