fix(ios): a failed devicectl uninstall must fail the reinstall

same hole as the simulator path: devicectl install over an app keeps its data, and the discarded uninstall error hid it. Uninstalling a bundle id that is not installed exits 0 with 'App uninstalled.' on a paired iPhone, so a failure here is always real.

internal/driver/ioscompanion/device.go

@@ -224,8 +224,14 @@ func (d *Driver) respawnDevice(ctx context.Context) error {
 // devicectlReinstall uninstalls then installs the app bundle via devicectl,
 // keyed on the CoreDevice id. App lifecycle stays with devicectl: the runner's
 // own install path is simulator-specific.
+// A failed uninstall ends the reinstall: installing over an app keeps its data,
+// so clear-state would be reported without happening. Uninstalling an app that
+// is not installed exits 0 ("App uninstalled." on a paired iPhone running iOS
+// 26.5), so there is no benign failure here to sort out from a real one.
 func (d *Driver) devicectlReinstall(ctx context.Context) error {
-	_ = exec.CommandContext(ctx, "xcrun", "devicectl", "device", "uninstall", "app", "--device", d.coreDeviceID, d.bundleID).Run()
+	if output, err := exec.CommandContext(ctx, "xcrun", "devicectl", "device", "uninstall", "app", "--device", d.coreDeviceID, d.bundleID).CombinedOutput(); err != nil {
+		return fmt.Errorf("devicectl uninstall %s: %w: %s", d.bundleID, err, strings.TrimSpace(string(output)))
+	}
 	output, err := exec.CommandContext(ctx, "xcrun", "devicectl", "device", "install", "app", "--device", d.coreDeviceID, d.appPath).CombinedOutput()
 	if err != nil {
 		return fmt.Errorf("devicectl install: %w: %s", err, strings.TrimSpace(string(output)))

internal/driver/ioscompanion/device_test.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"os/exec"
 	"slices"
+	"strings"
 	"testing"
 
 	"github.com/priyanshujain/sanderling/internal/driver/ioscompanion/transport"
@@ -182,6 +183,45 @@ func TestNewDeviceReinstallsOnceBeforeTheRunnerSession(t *testing.T) {
 	}
 }
 
+func TestDevicectlReinstallStopsWhenTheUninstallFails(t *testing.T) {
+	log := scriptedXcrun(t, `"devicectl device uninstall "*) echo "ERROR: Internal logic error: Connection was invalidated"; exit 1;;
+"devicectl device install "*) :;;`)
+	d := &Driver{coreDeviceID: "CORE-DEVICE", bundleID: "app.example", appPath: "/tmp/Sample.app"}
+
+	err := d.devicectlReinstall(context.Background())
+
+	if err == nil {
+		t.Fatal("devicectlReinstall reported success while app.example kept the data clear-state was asked to remove")
+	}
+	for _, want := range []string{"app.example", "Connection was invalidated"} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("error %q does not quote %q", err, want)
+		}
+	}
+	calls := xcrunCalls(t, log)
+	if slices.ContainsFunc(calls, func(call string) bool { return strings.HasPrefix(call, "devicectl device install") }) {
+		t.Errorf("xcrun calls = %v: installing over the app carries its data into the run", calls)
+	}
+}
+
+func TestDevicectlReinstallProceedsWhenNothingIsInstalled(t *testing.T) {
+	log := scriptedXcrun(t, `"devicectl device uninstall "*) echo "App uninstalled.";;
+"devicectl device install "*) :;;`)
+	d := &Driver{coreDeviceID: "CORE-DEVICE", bundleID: "app.example", appPath: "/tmp/Sample.app"}
+
+	if err := d.devicectlReinstall(context.Background()); err != nil {
+		t.Fatalf("devicectlReinstall: %v", err)
+	}
+
+	want := []string{
+		"devicectl device uninstall app --device CORE-DEVICE app.example",
+		"devicectl device install app --device CORE-DEVICE /tmp/Sample.app",
+	}
+	if got := xcrunCalls(t, log); !slices.Equal(got, want) {
+		t.Fatalf("xcrun calls = %v, want %v", got, want)
+	}
+}
+
 func TestDeviceClearStateWithoutAppPathWarnsOnce(t *testing.T) {
 	output := &bytes.Buffer{}
 	d := &Driver{output: output, deviceMode: true}