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/actions.rs

@@ -5448,12 +5448,13 @@ async fn handle_drag(cmd: &Value, state: &mut DaemonState) -> Result<Value, Stri
     mgr.client
         .send_command(
             "Input.dispatchMouseEvent",
-            Some(json!({ "type": "mousePressed", "x": sx, "y": sy, "button": "left", "clickCount": 1 })),
+            Some(json!({ "type": "mousePressed", "x": sx, "y": sy, "button": "left", "buttons": 1, "clickCount": 1 })),
             Some(&source_session_id),
         )
         .await?;
 
-    // Move in steps to target
+    // Move in steps to target, keeping the left button held (buttons: 1) so
+    // that the browser sees a drag rather than a plain pointer move.
     let steps = 10;
     for i in 1..=steps {
         let cx = sx + (tx - sx) * (i as f64) / (steps as f64);
@@ -5461,7 +5462,7 @@ async fn handle_drag(cmd: &Value, state: &mut DaemonState) -> Result<Value, Stri
         mgr.client
             .send_command(
                 "Input.dispatchMouseEvent",
-                Some(json!({ "type": "mouseMoved", "x": cx, "y": cy })),
+                Some(json!({ "type": "mouseMoved", "x": cx, "y": cy, "button": "left", "buttons": 1 })),
                 Some(&target_session_id),
             )
             .await?;
@@ -5472,7 +5473,7 @@ async fn handle_drag(cmd: &Value, state: &mut DaemonState) -> Result<Value, Stri
     mgr.client
         .send_command(
             "Input.dispatchMouseEvent",
-            Some(json!({ "type": "mouseReleased", "x": tx, "y": ty, "button": "left", "clickCount": 1 })),
+            Some(json!({ "type": "mouseReleased", "x": tx, "y": ty, "button": "left", "buttons": 0, "clickCount": 1 })),
             Some(&target_session_id),
         )
         .await?;

cli/src/native/e2e_tests.rs

@@ -1615,6 +1615,73 @@ async fn e2e_mouse_drag_reaches_pointer_capture_target() {
     assert_success(&resp);
 }
 
+#[tokio::test]
+#[ignore]
+async fn e2e_drag_action_sends_buttons_during_move() {
+    let mut state = DaemonState::new();
+
+    let resp = execute_command(
+        &json!({ "id": "1", "action": "launch", "headless": true }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+
+    let resp = execute_command(
+        &json!({
+            "id": "2",
+            "action": "navigate",
+            "url": native_test_fixture_url("html5_drag_probe")
+        }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+
+    let resp = execute_command(
+        &json!({
+            "id": "3",
+            "action": "drag",
+            "source": "#source",
+            "target": "#dest"
+        }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+    assert_eq!(get_data(&resp)["dragged"].as_bool(), Some(true));
+
+    let resp = execute_command(
+        &json!({ "id": "4", "action": "evaluate", "script": "window.__html5DragProbe" }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+
+    let probe = &get_data(&resp)["result"];
+    let events = probe["events"]
+        .as_array()
+        .expect("html5 drag probe should expose events");
+
+    // The mousemove events emitted while the button is held should carry
+    // buttons == 1 so the browser recognises the gesture as a drag.
+    assert!(
+        events
+            .iter()
+            .any(|event| { event["type"] == "mousemove" && event["buttons"].as_i64() == Some(1) }),
+        "Expected at least one mousemove with buttons == 1 during drag"
+    );
+
+    // dragstart must fire on the source element.
+    assert!(
+        events.iter().any(|event| event["type"] == "dragstart"),
+        "Expected dragstart to fire on the source element"
+    );
+
+    let resp = execute_command(&json!({ "id": "99", "action": "close" }), &mut state).await;
+    assert_success(&resp);
+}
+
 // ---------------------------------------------------------------------------
 // State save/load, state management
 // ---------------------------------------------------------------------------

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" => {