test: captured frames do not share memory with the SDK frame

The fake frames now hand out a buffer (memoryview) like pyrealsense2's
BufData, so np.asanyarray() of it is a view, as on the robot; a control test
proves it. Then: the captured rgb/depth share no memory with the fake SDK
frame and own their data (without the fix both shared it), and _owned()
copies views only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/fake_realsense.py

@@ -18,6 +18,11 @@ class FakeVideoFrame:
         self._data = data
 
     def get_data(self):
+        # A buffer over the frame's memory, as pyrealsense2's BufData: np.asanyarray() of it is a view.
+        return memoryview(self._data)
+
+    @property
+    def array(self) -> np.ndarray:
         return self._data
 
     def get_height(self) -> int:
@@ -54,6 +59,7 @@ class FakePipeline:
         self._active = 0
         self._lock = threading.Lock()
         self.stopped = False
+        self.last_frameset = None
 
     def wait_for_frames(self, timeout_ms: int = 5000):
         with self._lock:
@@ -63,7 +69,8 @@ class FakePipeline:
             index = self.calls
         try:
             time.sleep(self.latency_s)
-            return FakeFrameset(index)
+            self.last_frameset = FakeFrameset(index)
+            return self.last_frameset
         finally:
             with self._lock:
                 self._active -= 1