feat(scenegraph): add depth-based 3D positioning via pinhole projection

- Add bbox_depth_center position strategy in SceneGraphBuilder using depth
  at bbox centre and configurable camera_hfov_degrees for pinhole projection.
- Add optional depth_sensor_uuid to HabitatSimulatorConfig; create depth
  sensor spec alongside RGB sensor.
- Add camera_position/camera_rotation fields to RoomView; capture pose from
  sensor_states when depth sensor is available.
- Update flatten_room_views for backward compatibility with legacy tuple
  format.
- Wired in depth sensor and bbox_depth_center strategy in verification
  notebook.
- Add tests for depth sensor support and new position strategies.

tests/test_notebook_verification_static.py

@@ -1,11 +1,23 @@
 from __future__ import annotations
 
+import ast
 from pathlib import Path
 
 
 NOTEBOOK = Path(__file__).resolve().parents[1] / "notebooks" / "verification.py"
 
 
+def _find_calls(tree: ast.AST, func_name: str) -> list[ast.Call]:
+    """Find all Call nodes for a named function (simple name, not attribute)."""
+    return [
+        node
+        for node in ast.walk(tree)
+        if isinstance(node, ast.Call)
+        and isinstance(node.func, ast.Name)
+        and node.func.id == func_name
+    ]
+
+
 def test_verification_notebook_uses_scenegraph_query_api():
     source = NOTEBOOK.read_text()
 
@@ -20,7 +32,6 @@ def test_verification_notebook_uses_hash_codec_for_object_hashes():
     # the builder handles it internally.
     assert "bits_tensor_to_hash_bytes" not in source
     assert "np.packbits" not in source
-    assert "scene_graph.objects[_obj_id] = ObjectNode" not in source
 
 
 def test_verification_notebook_uses_scene_graph_builder():
@@ -30,4 +41,56 @@ def test_verification_notebook_uses_scene_graph_builder():
     assert "SceneGraphBuildConfig" in source
     assert "flatten_room_views" in source
     assert "scene_graph, build_artifacts = builder.build_from_room_views" in source
-    assert "scene_graph.objects[_obj_id] = ObjectNode" not in source
+
+    # Verify no direct ObjectNode construction (builder handles it internally)
+    tree = ast.parse(source)
+    object_node_calls = _find_calls(tree, "ObjectNode")
+    assert len(object_node_calls) == 0, (
+        "Notebook should not construct ObjectNode() directly; "
+        "the builder handles it"
+    )
+
+
+def test_verification_notebook_uses_bbox_depth_center_positioning():
+    source = NOTEBOOK.read_text()
+    tree = ast.parse(source)
+
+    # --- SceneGraphBuildConfig must use position_strategy='bbox_depth_center' ---
+    sg_config_calls = _find_calls(tree, "SceneGraphBuildConfig")
+    assert len(sg_config_calls) >= 1, (
+        "Notebook must instantiate SceneGraphBuildConfig"
+    )
+    config_kwargs = {
+        kw.arg: kw.value for kw in sg_config_calls[0].keywords if kw.arg is not None
+    }
+
+    assert "position_strategy" in config_kwargs
+    pos_val = config_kwargs["position_strategy"]
+    assert isinstance(pos_val, ast.Constant) and pos_val.value == "bbox_depth_center", (
+        f"Expected position_strategy='bbox_depth_center', got {pos_val!r}"
+    )
+
+    assert "camera_hfov_degrees" in config_kwargs, (
+        "SceneGraphBuildConfig should include camera_hfov_degrees"
+    )
+
+    # --- object_rows dict literals must include bbox_xyxy and position_confidence ---
+    found_bbox = False
+    found_pos_conf = False
+    for node in ast.walk(tree):
+        if isinstance(node, ast.Dict):
+            keys = {k.value for k in node.keys if isinstance(k, ast.Constant)}
+            if "obj_id" in keys:
+                if "bbox_xyxy" in keys:
+                    found_bbox = True
+                if "position_confidence" in keys:
+                    found_pos_conf = True
+
+    assert found_bbox, "object_rows must include bbox_xyxy column"
+    assert found_pos_conf, "object_rows must include position_confidence column"
+
+    # --- No direct ObjectNode( construction ---
+    object_node_calls = _find_calls(tree, "ObjectNode")
+    assert len(object_node_calls) == 0, (
+        "Notebook should not construct ObjectNode() directly"
+    )