fix(tabs): activate clicks when pointer release has no button (#6386)

Co-authored-by: Orca <help@stably.ai>

src/renderer/src/components/tab-bar/tab-strip-pointer-activation.test.tsx

@@ -65,8 +65,8 @@ function renderProbe(onActivate = vi.fn()): {
   }
 }
 
-function dispatchPointer(target: EventTarget, type: string): void {
-  target.dispatchEvent(new MouseEvent(type, { bubbles: true, button: 0 }))
+function dispatchPointer(target: EventTarget, type: string, button = 0): void {
+  target.dispatchEvent(new MouseEvent(type, { bubbles: true, button }))
 }
 
 afterEach(() => {
@@ -89,6 +89,16 @@ describe('useTabStripPointerActivation', () => {
     expect(onActivate).toHaveBeenCalledTimes(1)
   })
 
+  it('activates when the release event reports no changed button', () => {
+    const { onActivate, tabButton } = renderProbe()
+
+    act(() => dispatchPointer(tabButton, 'pointerdown'))
+    act(() => dispatchPointer(window, 'pointerup', -1))
+
+    expect(tabButton.dataset.pressed).toBe('false')
+    expect(onActivate).toHaveBeenCalledTimes(1)
+  })
+
   it('cancels pending activation on pointercancel', () => {
     const { onActivate, tabButton } = renderProbe()
 

src/renderer/src/components/tab-bar/tab-strip-pointer-activation.ts

@@ -33,10 +33,9 @@ export function useTabStripPointerActivation({
     if (!isPressed) {
       return
     }
-    const finishPointerPress = (event: PointerEvent): void => {
-      if (event.button !== 0) {
-        return
-      }
+    const finishPointerPress = (): void => {
+      // Why: pointerup often reports button -1/no changed button; the left-button
+      // gate is on pointerdown, so release must always clear the pending click.
       const shouldActivate = pendingActivationRef.current && !isTabDragActiveRef.current
       pendingActivationRef.current = false
       setIsPressed(false)