fix(tvos): stop a single Siri Remote flick moving focus two steps

Touch travel banked during the swipe repeat cooldown was released as a
second focus step by the first post-cooldown move frame, even when the
finger had stopped or was lifting. Re-anchor the swipe delta on every
frame inside the cooldown so a discrete flick emits exactly one step
while a sustained drag keeps repeating.

close #1756

lib/services/apple_tv_remote_touch_service.dart

@@ -172,12 +172,19 @@ class AppleTvRemoteTouchService {
 
     final deltaX = _anchorX - x;
     final deltaY = _anchorY - y;
-    final axis = _resolveSwipeAxis(x: x, y: y, deltaX: deltaX, deltaY: deltaY);
-    if (axis == null) return;
 
     final now = _now();
     final lastSwipeAt = _lastSwipeAt;
     if (lastSwipeAt != null && now.difference(lastSwipeAt) < swipeRepeatInterval) {
+      // Travel during the repeat cooldown never counts toward the next step:
+      // re-anchor on every frame so a fast flick's deceleration tail is
+      // discarded instead of banked. Without this, the first post-cooldown
+      // move frame — even a stationary or lift-drift one — released the
+      // banked delta as a second focus step for a single intentional swipe.
+      // A deliberate continuous drag still repeats because it covers a fresh
+      // swipe threshold after each cooldown expires.
+      _anchorX = x;
+      _anchorY = y;
       final age = now.difference(lastSwipeAt).inMilliseconds;
       _log(
         'suppress swipe reason=repeat-cooldown age=${age}ms dx=${_formatDouble(deltaX)} dy=${_formatDouble(deltaY)}',
@@ -185,6 +192,9 @@ class AppleTvRemoteTouchService {
       return;
     }
 
+    final axis = _resolveSwipeAxis(x: x, y: y, deltaX: deltaX, deltaY: deltaY);
+    if (axis == null) return;
+
     final logicalKey = axis == _SwipeAxis.horizontal
         ? (deltaX >= 0 ? LogicalKeyboardKey.arrowLeft : LogicalKeyboardKey.arrowRight)
         : (deltaY >= 0 ? LogicalKeyboardKey.arrowUp : LogicalKeyboardKey.arrowDown);

test/services/apple_tv_remote_touch_service_test.dart

@@ -6,7 +6,7 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
   group('AppleTvRemoteTouchService', () {
-    test('emits repeated horizontal swipes only after the repeat interval', () async {
+    test('a single fast flick emits exactly one swipe', () async {
       final harness = _Harness();
 
       await harness.send('started', x: 500, y: 500);
@@ -15,8 +15,44 @@ void main() {
 
       expect(harness.keys, [LogicalKeyboardKey.arrowLeft]);
 
+      // The flick's tail travel landed inside the repeat cooldown and must be
+      // discarded: a near-stationary frame after the cooldown expires must not
+      // release it as a second focus step.
       harness.advance(const Duration(milliseconds: 141));
-      await harness.send('move', x: 260, y: 490);
+      await harness.send('move', x: 259, y: 490);
+
+      expect(harness.keys, [LogicalKeyboardKey.arrowLeft]);
+    });
+
+    test('sub-threshold cooldown travel plus lift drift does not fire a second swipe', () async {
+      final harness = _Harness();
+
+      await harness.send('started', x: 500, y: 500);
+      await harness.send('move', x: 390, y: 500);
+      // 80pt tail inside the cooldown: below threshold, but banked it would
+      // combine with the 70pt lift drift below to cross the 100pt threshold.
+      await harness.send('move', x: 310, y: 500);
+
+      harness.advance(const Duration(milliseconds: 141));
+      await harness.send('move', x: 240, y: 500);
+
+      expect(harness.keys, [LogicalKeyboardKey.arrowLeft]);
+    });
+
+    test('a sustained drag keeps repeating after each repeat interval', () async {
+      final harness = _Harness();
+
+      await harness.send('started', x: 900, y: 500);
+      await harness.send('move', x: 780, y: 500);
+
+      expect(harness.keys, [LogicalKeyboardKey.arrowLeft]);
+
+      harness.advance(const Duration(milliseconds: 70));
+      await harness.send('move', x: 700, y: 500);
+
+      // A full fresh threshold is covered after the cooldown expires.
+      harness.advance(const Duration(milliseconds: 71));
+      await harness.send('move', x: 580, y: 500);
 
       expect(harness.keys, [LogicalKeyboardKey.arrowLeft, LogicalKeyboardKey.arrowLeft]);
     });