feat(perception): measure M48S load envelope

tests/test_perception_graph.py

@@ -835,6 +835,50 @@ def test_recorded_source_reuses_one_timeline_for_1x_and_uncapped(tmp_path: Path)
     assert one_x[1].registered_point_increment_payload is None
 
 
+def test_recorded_source_target_rate_changes_only_wall_clock_pacing(tmp_path: Path) -> None:
+    camera_path, timeline_path = _write_recorded_fixture(tmp_path)
+    now = [1_000_000_000]
+    waits: list[float] = []
+
+    def wait(stop_event: Event, seconds: float) -> bool:
+        waits.append(seconds)
+        now[0] += round(seconds * 1_000_000_000)
+        return stop_event.is_set()
+
+    source = RecordedRavnoves00Source(
+        camera_index_path=camera_path,
+        source_pack_path=timeline_path,
+        pacing=ReplayPacing.ONE_X,
+        target_rate_hz=20.0,
+        expected_frame_count=2,
+        expected_source_pack_sha256=None,
+        clock_ns=lambda: now[0],
+        wait=wait,
+    )
+
+    packets = list(source.packets(Event()))
+
+    assert waits == pytest.approx([0.05])
+    assert (
+        packets[1].envelope.timestamps.source_ns
+        - packets[0].envelope.timestamps.source_ns
+        == 100_000_000
+    )
+
+
+def test_recorded_source_rejects_target_rate_for_uncapped_replay(tmp_path: Path) -> None:
+    camera_path, timeline_path = _write_recorded_fixture(tmp_path)
+    with pytest.raises(RecordedSourceError, match="requires paced replay"):
+        RecordedRavnoves00Source(
+            camera_index_path=camera_path,
+            source_pack_path=timeline_path,
+            pacing=ReplayPacing.UNCAPPED,
+            target_rate_hz=12.0,
+            expected_frame_count=2,
+            expected_source_pack_sha256=None,
+        )
+
+
 def test_recorded_source_rejects_timeline_mismatch(tmp_path: Path) -> None:
     camera_path, timeline_path = _write_recorded_fixture(tmp_path, mismatched=True)
     source = RecordedRavnoves00Source(