feat(layout): add pointer cancel handling to ActivityBar and improve drag end detection in TabBar

- Implemented a new `handlePointerCancel` function in the ActivityBar to manage pointer cancellation events, enhancing drag-and-drop interactions.
- Updated the TabBar component to utilize a callback for detecting drag end proximity to the tab strip, improving the user experience during tab management.

src/components/layout/ActivityBar.tsx

@@ -326,6 +326,22 @@ function DropZone({
     [requestPointerDrop, resetDragState],
   );
 
+  const handlePointerCancel = useCallback(
+    (event: PointerEvent) => {
+      const state = pointerDragRef.current;
+      if (!state || state.pointerId !== event.pointerId) return;
+
+      if (event.currentTarget.hasPointerCapture(event.pointerId)) {
+        event.currentTarget.releasePointerCapture(event.pointerId);
+      }
+      resetDragState();
+      window.setTimeout(() => {
+        suppressClickRef.current = false;
+      }, 0);
+    },
+    [resetDragState],
+  );
+
   const handleDragStart = useCallback(
     (e: DragEvent, itemId: string) => {
       dragItemIdRef.current = itemId;
@@ -402,6 +418,7 @@ function DropZone({
           onPointerDown={(e) => handlePointerDown(e, item.id)}
           onPointerMove={handlePointerMove}
           onPointerEnd={handlePointerEnd}
+          onPointerCancel={handlePointerCancel}
           draggable={!usePointerDrag}
           suppressClickRef={suppressClickRef}
           showDropIndicator={dropIndex === idx}
@@ -439,6 +456,7 @@ function ActivityBarButton({
   onPointerDown,
   onPointerMove,
   onPointerEnd,
+  onPointerCancel,
   draggable,
   suppressClickRef,
   showDropIndicator,
@@ -461,6 +479,7 @@ function ActivityBarButton({
   onPointerDown: (e: PointerEvent) => void;
   onPointerMove: (e: PointerEvent) => void;
   onPointerEnd: (e: PointerEvent) => void;
+  onPointerCancel: (e: PointerEvent) => void;
   draggable: boolean;
   suppressClickRef: MutableRefObject<boolean>;
   showDropIndicator: boolean;
@@ -483,7 +502,7 @@ function ActivityBarButton({
               onPointerDown={onPointerDown}
               onPointerMove={onPointerMove}
               onPointerUp={onPointerEnd}
-              onPointerCancel={onPointerEnd}
+              onPointerCancel={onPointerCancel}
               className={`relative flex flex-col items-center justify-center w-full transition-colors ${showLabel ? "min-h-12 gap-0.5 py-1" : "h-9"}`}
               style={{
                 color: active ? "var(--df-primary)" : "var(--df-text-muted)",

src/components/terminal/TabBar.tsx

@@ -710,6 +710,22 @@ function TabBar({
     [tabs],
   );
 
+  const isDragEndFallbackNearTabStrip = useCallback((clientX: number, clientY: number) => {
+    const strip = tabStripRef.current;
+    if (!strip || clientX === 0) return false;
+
+    const rect = strip.getBoundingClientRect();
+    const horizontalTolerance = 48;
+    const verticalTolerance = Math.max(96, rect.height * 3);
+    const isWithinHorizontalRange =
+      clientX >= rect.left - horizontalTolerance && clientX <= rect.right + horizontalTolerance;
+    if (!isWithinHorizontalRange) return false;
+
+    if (clientY === 0) return true;
+
+    return clientY >= rect.top - verticalTolerance && clientY <= rect.bottom + verticalTolerance;
+  }, []);
+
   const handleDropAtIndex = useCallback(
     (insertionIndex: number, event?: DragEvent<HTMLDivElement>) => {
       const externalTabId = event?.dataTransfer.getData("application/nyaterm-tab");
@@ -759,20 +775,9 @@ function TabBar({
     }
 
     const fallbackTabId = draggedTabIdRef.current;
-    const strip = tabStripRef.current;
-    if (fallbackTabId && strip && event.clientX !== 0) {
-      const rect = strip.getBoundingClientRect();
-      const horizontalTolerance = 48;
-      const verticalTolerance = 16;
-      const isNearTabStrip =
-        event.clientX >= rect.left - horizontalTolerance &&
-        event.clientX <= rect.right + horizontalTolerance &&
-        event.clientY >= rect.top - verticalTolerance &&
-        event.clientY <= rect.bottom + verticalTolerance;
-      if (isNearTabStrip) {
-        handleDropAtIndex(getInsertionIndexFromClientX(event.clientX));
-        return;
-      }
+    if (fallbackTabId && isDragEndFallbackNearTabStrip(event.clientX, event.clientY)) {
+      handleDropAtIndex(getInsertionIndexFromClientX(event.clientX));
+      return;
     }
 
     resetDragState();