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_introspection.py

@@ -0,0 +1,156 @@
+"""
+Tests for PipelineIntrospectionSource.
+"""
+
+from engine.pipeline_sources.pipeline_introspection import PipelineIntrospectionSource
+
+
+class TestPipelineIntrospectionSource:
+    """Tests for PipelineIntrospectionSource."""
+
+    def test_basic_init(self):
+        """Source initializes with defaults."""
+        source = PipelineIntrospectionSource()
+        assert source.name == "pipeline-inspect"
+        assert source.is_dynamic is True
+        assert source.frame == 0
+
+    def test_init_with_pipelines(self):
+        """Source initializes with custom pipelines list."""
+        source = PipelineIntrospectionSource(
+            pipelines=[], viewport_width=100, viewport_height=40
+        )
+        assert source.viewport_width == 100
+        assert source.viewport_height == 40
+
+    def test_inlet_outlet_types(self):
+        """Source has correct inlet/outlet types."""
+        source = PipelineIntrospectionSource()
+        # inlet should be NONE (source), outlet should be SOURCE_ITEMS
+        from engine.pipeline.core import DataType
+
+        assert DataType.NONE in source.inlet_types
+        assert DataType.SOURCE_ITEMS in source.outlet_types
+
+    def test_fetch_returns_items(self):
+        """fetch() returns SourceItem list."""
+        source = PipelineIntrospectionSource()
+        items = source.fetch()
+        assert len(items) == 1
+        assert items[0].source == "pipeline-inspect"
+
+    def test_fetch_increments_frame(self):
+        """fetch() increments frame counter."""
+        source = PipelineIntrospectionSource()
+        assert source.frame == 0
+        source.fetch()
+        assert source.frame == 1
+        source.fetch()
+        assert source.frame == 2
+
+    def test_get_items(self):
+        """get_items() returns list of SourceItems."""
+        source = PipelineIntrospectionSource()
+        items = source.get_items()
+        assert isinstance(items, list)
+        assert len(items) > 0
+        assert items[0].source == "pipeline-inspect"
+
+    def test_add_pipeline(self):
+        """add_pipeline() adds pipeline to list."""
+        source = PipelineIntrospectionSource()
+        mock_pipeline = object()
+        source.add_pipeline(mock_pipeline)
+        assert mock_pipeline in source._pipelines
+
+    def test_remove_pipeline(self):
+        """remove_pipeline() removes pipeline from list."""
+        source = PipelineIntrospectionSource()
+        mock_pipeline = object()
+        source.add_pipeline(mock_pipeline)
+        source.remove_pipeline(mock_pipeline)
+        assert mock_pipeline not in source._pipelines
+
+
+class TestPipelineIntrospectionRender:
+    """Tests for rendering methods."""
+
+    def test_render_header_no_pipelines(self):
+        """_render_header returns default when no pipelines."""
+        source = PipelineIntrospectionSource()
+        lines = source._render_header()
+        assert len(lines) == 1
+        assert "PIPELINE INTROSPECTION" in lines[0]
+
+    def test_render_bar(self):
+        """_render_bar creates correct bar."""
+        source = PipelineIntrospectionSource()
+        bar = source._render_bar(50, 10)
+        assert len(bar) == 10
+        assert bar.count("█") == 5
+        assert bar.count("░") == 5
+
+    def test_render_bar_zero(self):
+        """_render_bar handles zero percentage."""
+        source = PipelineIntrospectionSource()
+        bar = source._render_bar(0, 10)
+        assert bar == "░" * 10
+
+    def test_render_bar_full(self):
+        """_render_bar handles 100%."""
+        source = PipelineIntrospectionSource()
+        bar = source._render_bar(100, 10)
+        assert bar == "█" * 10
+
+    def test_render_sparkline(self):
+        """_render_sparkline creates sparkline."""
+        source = PipelineIntrospectionSource()
+        values = [1.0, 2.0, 3.0, 4.0, 5.0]
+        sparkline = source._render_sparkline(values, 10)
+        assert len(sparkline) == 10
+
+    def test_render_sparkline_empty(self):
+        """_render_sparkline handles empty values."""
+        source = PipelineIntrospectionSource()
+        sparkline = source._render_sparkline([], 10)
+        assert sparkline == " " * 10
+
+    def test_render_footer_no_pipelines(self):
+        """_render_footer shows collecting data when no pipelines."""
+        source = PipelineIntrospectionSource()
+        lines = source._render_footer()
+        assert len(lines) >= 2
+        assert "collecting data" in lines[1] or "Frame Time" in lines[0]
+
+
+class TestPipelineIntrospectionFull:
+    """Integration tests."""
+
+    def test_render_empty(self):
+        """_render works with no pipelines."""
+        source = PipelineIntrospectionSource()
+        lines = source._render()
+        assert len(lines) > 0
+        assert "PIPELINE INTROSPECTION" in lines[0]
+
+    def test_render_with_mock_pipeline(self):
+        """_render works with mock pipeline."""
+        source = PipelineIntrospectionSource()
+
+        class MockStage:
+            category = "source"
+            name = "test"
+
+        class MockPipeline:
+            stages = {"test": MockStage()}
+            execution_order = ["test"]
+
+            def get_metrics_summary(self):
+                return {"stages": {"test": {"avg_ms": 1.5}}, "avg_ms": 2.0, "fps": 60}
+
+            def get_frame_times(self):
+                return [1.0, 2.0, 3.0]
+
+        source.add_pipeline(MockPipeline())
+        lines = source._render()
+        assert len(lines) > 0