feat: add pipeline introspection demo mode

- Add PipelineIntrospectionSource that renders live ASCII DAG with metrics
- Add PipelineMetricsSensor exposing pipeline performance as sensor values
- Add PipelineIntrospectionDemo controller with 3-phase animation:
  - Phase 1: Toggle effects one at a time (3s each)
  - Phase 2: LFO drives intensity default→max→min→default
  - Phase 3: All effects with shared LFO (infinite loop)
- Add pipeline-inspect preset
- Add get_frame_times() to Pipeline for sparkline data
- Add tests for new components
- Update mise.toml with pipeline-inspect preset task

tests/test_pipeline_metrics_sensor.py

@@ -0,0 +1,113 @@
+"""
+Tests for PipelineMetricsSensor.
+"""
+
+from engine.sensors.pipeline_metrics import PipelineMetricsSensor
+
+
+class MockPipeline:
+    """Mock pipeline for testing."""
+
+    def __init__(self, metrics=None):
+        self._metrics = metrics or {}
+
+    def get_metrics_summary(self):
+        return self._metrics
+
+
+class TestPipelineMetricsSensor:
+    """Tests for PipelineMetricsSensor."""
+
+    def test_basic_init(self):
+        """Sensor initializes with defaults."""
+        sensor = PipelineMetricsSensor()
+        assert sensor.name == "pipeline"
+        assert sensor.available is False
+
+    def test_init_with_pipeline(self):
+        """Sensor initializes with pipeline."""
+        mock = MockPipeline()
+        sensor = PipelineMetricsSensor(mock)
+        assert sensor.available is True
+
+    def test_set_pipeline(self):
+        """set_pipeline() updates pipeline."""
+        sensor = PipelineMetricsSensor()
+        assert sensor.available is False
+        sensor.set_pipeline(MockPipeline())
+        assert sensor.available is True
+
+    def test_read_no_pipeline(self):
+        """read() returns None when no pipeline."""
+        sensor = PipelineMetricsSensor()
+        assert sensor.read() is None
+
+    def test_read_with_metrics(self):
+        """read() returns sensor value with metrics."""
+        mock = MockPipeline(
+            {
+                "total_ms": 18.5,
+                "fps": 54.0,
+                "avg_ms": 18.5,
+                "min_ms": 15.0,
+                "max_ms": 22.0,
+                "stages": {"render": {"avg_ms": 12.0}, "noise": {"avg_ms": 3.0}},
+            }
+        )
+        sensor = PipelineMetricsSensor(mock)
+        val = sensor.read()
+        assert val is not None
+        assert val.sensor_name == "pipeline"
+        assert val.value == 18.5
+
+    def test_read_with_error(self):
+        """read() returns None when metrics have error."""
+        mock = MockPipeline({"error": "No metrics collected"})
+        sensor = PipelineMetricsSensor(mock)
+        assert sensor.read() is None
+
+    def test_get_stage_timing(self):
+        """get_stage_timing() returns stage timing."""
+        mock = MockPipeline(
+            {
+                "stages": {"render": {"avg_ms": 12.0}, "noise": {"avg_ms": 3.0}},
+            }
+        )
+        sensor = PipelineMetricsSensor(mock)
+        assert sensor.get_stage_timing("render") == 12.0
+        assert sensor.get_stage_timing("noise") == 3.0
+        assert sensor.get_stage_timing("nonexistent") == 0.0
+
+    def test_get_stage_timing_no_pipeline(self):
+        """get_stage_timing() returns 0 when no pipeline."""
+        sensor = PipelineMetricsSensor()
+        assert sensor.get_stage_timing("test") == 0.0
+
+    def test_get_all_timings(self):
+        """get_all_timings() returns all stage timings."""
+        mock = MockPipeline(
+            {
+                "stages": {"render": {"avg_ms": 12.0}, "noise": {"avg_ms": 3.0}},
+            }
+        )
+        sensor = PipelineMetricsSensor(mock)
+        timings = sensor.get_all_timings()
+        assert timings == {"render": {"avg_ms": 12.0}, "noise": {"avg_ms": 3.0}}
+
+    def test_get_frame_history(self):
+        """get_frame_history() returns frame times."""
+        MockPipeline()
+
+        class MockPipelineWithFrames:
+            def get_frame_times(self):
+                return [1.0, 2.0, 3.0]
+
+        sensor = PipelineMetricsSensor(MockPipelineWithFrames())
+        history = sensor.get_frame_history()
+        assert history == [1.0, 2.0, 3.0]
+
+    def test_start_stop(self):
+        """start() and stop() work."""
+        sensor = PipelineMetricsSensor()
+        assert sensor.start() is True
+        sensor.stop()  # Should not raise