fix: include buttons bitmask in drag mouseMoved events (#1087)

* fix: include buttons bitmask in drag mouseMoved events

The drag handler was omitting the `buttons` field from every
`mouseMoved` event dispatched during the move phase.  Without it the
browser sees `event.buttons === 0`, meaning no button is held, so
`dragstart`/`dragover`/`drop` never fire and the drop target never
receives the element.

Fix:
- Add `"buttons": 1` (left-button mask) to each `mouseMoved` sent
  while the button is held.
- Add `"buttons": 1` to `mousePressed` and `"buttons": 0` to
  `mouseReleased`, consistent with how `dispatch_click` handles the
  same fields in interaction.rs.
- Correct the parity-test fixture for `drag`, which was supplying a
  `selector` key instead of the `source` key that `handle_drag` reads.
- Add an e2e test (`e2e_drag_action_sends_buttons_during_move`) that
  drives the high-level `drag` action against the existing
  `html5_drag_probe` fixture and asserts that `mousemove` events carry
  `buttons == 1` and that `dragstart` fires on the source element.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* style: fix rustfmt formatting in e2e drag test

---------

Co-authored-by: wangjingjing <wangjingjing.99@bytedance.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: ctate <366502+ctate@users.noreply.github.com>

cli/src/native/parity_tests.rs

@@ -344,7 +344,7 @@ fn minimal_command(action: &str, id: &str) -> Value {
             obj.insert("script".to_string(), json!("h => h"));
         }
         "drag" => {
-            obj.insert("selector".to_string(), json!("body"));
+            obj.insert("source".to_string(), json!("body"));
             obj.insert("target".to_string(), json!("body"));
         }
         "swipe" => {