Present replay 3D with the cursor and open Analyze on a remembered video

Replay left the 3D pane on the rest mesh or a sparse overlay, and Analyze skipped the setup dialog unless the file was re-picked. Live Run no longer starts a chain on a video path. Verified with Studio tests for flush, overlay mask, Analyze open, live-video refusal, and locales.

apps/studio/tests/test_scene3d_adapters.py

@@ -173,6 +173,36 @@ def test_the_finger_adapter_publishes_a_field_already_in_the_domain(scene):
     )
 
 
+def test_a_recovered_flow_keeps_the_island_as_the_overlay_mask(scene):
+    """Replay flow is finite only at stored cells; the overlay mask must stay the island.
+
+    The selector already drops ``NaN`` samples. If the mask is those finite cells too,
+    an arrow tip one neighbour over is rejected and 3D keeps a handful of rim dots
+    while 2D draws the full grid.
+    """
+    adapter = FingerFrameAdapter(
+        geometry_id=scene.geometry_id,
+        field_domain_id=scene.field_domain_id,
+        shape_hw=scene.shape_hw,
+    )
+    h, w = scene.shape_hw
+    flow = np.full((h, w, 2), np.nan, dtype=np.float32)
+    flow[1, 1, 0] = 7.0
+    island = np.ones((h, w), dtype=bool)
+    depth = np.zeros((h, w), dtype=np.float32)
+    frame = adapter.snapshot(
+        FakePacket(flow=flow, depth=depth, valid_mask=island),
+        runtime=None,
+        identity=_identity(),
+    )
+    assert frame is not None
+    assert frame.flow_uv is not None and frame.flow_valid_mask is not None
+    mask = np.asarray(frame.flow_valid_mask)
+    assert mask.all(), "the overlay mask shrank to the recovered sample cells"
+    finite = np.isfinite(np.asarray(frame.flow_uv)[..., 0])
+    assert int(finite.sum()) == 1
+
+
 def test_the_finger_adapter_remaps_through_the_unroll_map():
     map_x = np.array([[0, 1, 2], [0, 1, 2], [0, 1, 2]], dtype=np.float32)
     map_y = np.array([[2, 2, 2], [1, 1, 1], [0, 0, 0]], dtype=np.float32)