fix(viz): narrow uniform test except + lock write

data_only_viz/action_head_pub.py

@@ -155,7 +155,8 @@ class ActionHeadPublisher(threading.Thread):
                 rkp = getattr(self.state, "right_hand_kp", None)
                 hands = [h for h in (lkp, rkp) if h is not None and len(h) > 0]
         feats = self._hand_ext.step(hands)
-        self.state.hand_feats = feats
+        with self.state.lock():
+            self.state.hand_feats = feats
         self.bridge.send_hands(feats, t_now)
 
     def _read_sources(self) -> tuple[

data_only_viz/tests/test_renderer_uniforms.py

@@ -19,7 +19,7 @@ def test_uniform_constants():
         assert UNIFORM_FLOATS == 24, f"expected 24, got {UNIFORM_FLOATS}"
         assert UNIFORM_SIZE == 96, f"expected 96, got {UNIFORM_SIZE}"
         assert struct.calcsize(f"{UNIFORM_FLOATS}f") == 96
-    except Exception as exc:  # pyobjc/Metal unavailable headless
+    except ImportError as exc:  # pyobjc/Metal unavailable headless
         # Fallback: at minimum the struct math is correct
         import pytest
         pytest.skip(f"renderer import skipped headless ({exc}); struct layout verified by test_uniform_layout_struct")