fix(ui): start pointer drags only while the primary button is held (#1071)

On macOS, with an editable element focused and an input method active, WebKit can deliver a tap as pointerup then pointerdown, so drag trackers saw every later pointermove as a held button: one tap plus a pointer move started a phantom drag (file drag label, tab detach, tool window move) and the next tap dropped it. A drag now starts only from a move with the primary button down, a move without it cancels the press, and late button-less moves after a drag started are ignored so the drop is kept. Resizers, dialog drag/resize, pan and the review gutter end instead; the Project view also listens for pointercancel.

Refs #760

Co-authored-by: ntbang0901 <[email protected]>

src/features/vcs/reviewGutter.ts

@@ -252,6 +252,7 @@ export function reviewGutter(handlers: ReviewGutterHandlers): Extension {
   const startDrag = (view: EditorView, drag: Drag) => {
     view.dispatch({ effects: setDrag.of(drag) });
     const move = (e: MouseEvent) => {
+      if (!(e.buttons & 1)) return up();
       const line = lineAtY(view, e.clientY);
       const cur = view.state.field(field).drag;
       if (line === null || !cur) return;