refactor(runner): narrow gesture clamp to the top shade strip

3-button nav (forced for every run) disables the side back and bottom home
gestures at the OS level. On-device probing confirmed side and bottom swipe
origins no longer drift, leaving the notification shade as the only edge
gesture a swipe can trigger. Clamp only the top strip; keep origin and
destination on screen otherwise.

internal/runner/runner.go

@@ -768,21 +768,20 @@ func screenBounds(tree *hierarchy.Tree) hierarchy.Bounds {
 	return bounds
 }
 
-// clampGestureToSafeArea keeps a swipe's origin out of the system gesture zones
+// clampGestureToSafeArea keeps a swipe's origin below the top status strip,
-// at the screen edges. A gesture that starts in the top strip pulls down the
+// where a downward drag pulls the notification shade over the app. Runs force
-// notification shade; the bottom strip is the home gesture and the side strips
+// 3-button navigation (ForceThreeButtonNav), which disables the side back and
-// are the back gesture. Any of these drags the fuzzer out of the app. The
+// bottom home gestures at the OS level; on-device probing confirmed side and
-// destination only needs to stay on screen. With an unknown screen size the
+// bottom origins then no longer drift, so the shade is the only edge gesture a
-// coordinates pass through unchanged.
+// swipe can still trigger. Origin and destination are otherwise only kept on
+// screen. With an unknown screen size the coordinates pass through unchanged.
 func clampGestureToSafeArea(fromX, fromY, toX, toY int, screen hierarchy.Bounds) (int, int, int, int) {
 	width, height := screen.Width(), screen.Height()
 	if width <= 0 || height <= 0 {
 		return fromX, fromY, toX, toY
 	}
-	// Margins are a fraction of each axis so they scale across devices and
+	// The top margin clears the status bar; calibrated as a fraction of height
-	// densities. The vertical margin clears the status bar (calibrated: swipes
+	// so swipes from below ~8% of height no longer open the shade.
-	// from below ~7% of height no longer open the shade) and the home gesture.
-	marginX := width / 20
 	marginY := height / 12
 	clamp := func(value, low, high int) int {
 		if value < low {
@@ -793,8 +792,8 @@ func clampGestureToSafeArea(fromX, fromY, toX, toY int, screen hierarchy.Bounds)
 		}
 		return value
 	}
-	fromX = clamp(fromX, screen.Left+marginX, screen.Right-marginX)
+	fromX = clamp(fromX, screen.Left, screen.Right)
-	fromY = clamp(fromY, screen.Top+marginY, screen.Bottom-marginY)
+	fromY = clamp(fromY, screen.Top+marginY, screen.Bottom)
 	toX = clamp(toX, screen.Left, screen.Right)
 	toY = clamp(toY, screen.Top, screen.Bottom)
 	return fromX, fromY, toX, toY

internal/runner/runner_test.go

@@ -1805,34 +1805,50 @@ func TestAwaitForeground_RelaunchesThenWaitsForWindow(t *testing.T) {
 	}
 }
 
-// TestClampGestureToSafeArea_KeepsOriginOutOfGestureZones locks the swipe fix:
+// TestClampGestureToSafeArea_KeepsOriginBelowShadeStrip locks the swipe fix: a
-// a gesture origin in the top status-bar strip pulls down the notification
+// gesture origin in the top status-bar strip pulls down the notification shade
-// shade and drags the fuzzer out of the app. The origin must be pulled into the
+// and drags the fuzzer out of the app. The origin must be pushed below the top
-// safe inner area while the destination only stays on screen.
+// margin. The side and bottom strips are NOT clamped: runs force 3-button
-func TestClampGestureToSafeArea_KeepsOriginOutOfGestureZones(t *testing.T) {
+// navigation, which disables the back and home gestures, so (verified on device)
+// those origins no longer drift.
+func TestClampGestureToSafeArea_KeepsOriginBelowShadeStrip(t *testing.T) {
 	screen := hierarchy.Bounds{Left: 0, Top: 0, Right: 1080, Bottom: 2400}
-	// marginX = 1080/20 = 54, marginY = 2400/12 = 200.
+	// marginY = 2400/12 = 200.
 
-	// The real shade-opening swipe captured on device: origin y=62 is pulled to
+	// The real shade-opening swipe captured on device: origin y=62 is pushed to
 	// the top margin (200); the in-range destination is untouched.
 	fromX, fromY, toX, toY := clampGestureToSafeArea(802, 62, 802, 447, screen)
 	if fromX != 802 || fromY != 200 || toX != 802 || toY != 447 {
-		t.Errorf("origin not clamped to the safe area: from=(%d,%d) to=(%d,%d), want from=(802,200) to=(802,447)", fromX, fromY, toX, toY)
+		t.Errorf("origin not pushed below the shade strip: from=(%d,%d) to=(%d,%d), want from=(802,200) to=(802,447)", fromX, fromY, toX, toY)
 	}
 
-	// Top-left corner origin pulled inside both margins.
+	// A side origin (left/right edge) passes through untouched: 3-button nav
-	fromX, fromY, _, _ = clampGestureToSafeArea(0, 0, 540, 1200, screen)
+	// disables the back gesture, so only the top y is clamped.
-	if fromX != 54 || fromY != 200 {
+	fromX, fromY, _, _ = clampGestureToSafeArea(5, 1200, 540, 1200, screen)
-		t.Errorf("corner origin not clamped to (54,200), got (%d,%d)", fromX, fromY)
+	if fromX != 5 || fromY != 1200 {
+		t.Errorf("side origin must pass through, got (%d,%d), want (5,1200)", fromX, fromY)
 	}
 
-	// An off-screen destination is clamped onto the screen (the destination only
+	// A bottom origin passes through (home gesture disabled by 3-button nav);
-	// needs to stay on screen, not inside the gesture margins).
+	// only the top edge is a hazard.
+	fromX, fromY, _, _ = clampGestureToSafeArea(540, 2399, 540, 1200, screen)
+	if fromX != 540 || fromY != 2399 {
+		t.Errorf("bottom origin must pass through, got (%d,%d), want (540,2399)", fromX, fromY)
+	}
+
+	// An off-screen destination is clamped onto the screen.
 	_, _, toX, toY = clampGestureToSafeArea(540, 1200, -50, 9999, screen)
 	if toX != 0 || toY != 2400 {
 		t.Errorf("off-screen destination not clamped to screen edges: got (%d,%d), want (0,2400)", toX, toY)
 	}
 
+	// An off-screen origin x is pulled back on screen even though it is not in a
+	// gesture zone.
+	fromX, _, _, _ = clampGestureToSafeArea(-30, 1200, 540, 1200, screen)
+	if fromX != 0 {
+		t.Errorf("off-screen origin x must clamp to 0, got %d", fromX)
+	}
+
 	// Unknown screen size leaves coordinates untouched.
 	fromX, fromY, toX, toY = clampGestureToSafeArea(802, 62, 802, 447, hierarchy.Bounds{})
 	if fromX != 802 || fromY != 62 || toX != 802 || toY != 447 {