feat(figment): complete pipeline integration with native effect plugin

- Add engine/effects/plugins/figment.py (native pipeline implementation)
- Add engine/figment_render.py, engine/figment_trigger.py, engine/themes.py
- Add 3 SVG assets in figments/ (Mexican/Aztec motif)
- Add engine/display/backends/animation_report.py for debugging
- Add engine/pipeline/adapters/frame_capture.py for frame capture
- Add test-figment preset to presets.toml
- Add cairosvg optional dependency to pyproject.toml
- Update EffectPluginStage to support is_overlay attribute (for overlay effects)
- Add comprehensive tests: test_figment_effect.py, test_figment_pipeline.py, test_figment_render.py
- Remove obsolete test_ui_simple.py
- Update TODO.md with test cleanup plan
- Refactor test_adapters.py to use real components instead of mocks

This completes the figment SVG overlay feature integration using the modern pipeline architecture, avoiding legacy effects_plugins. All tests pass (758 total).

tests/test_figment_render.py

@@ -0,0 +1,104 @@
+"""
+Tests to verify figment rendering in the pipeline.
+"""
+
+from engine.effects.plugins import discover_plugins
+from engine.effects.registry import get_registry
+from engine.effects.types import EffectConfig
+from engine.pipeline import Pipeline, PipelineConfig
+from engine.pipeline.adapters import (
+    EffectPluginStage,
+    SourceItemsToBufferStage,
+    create_stage_from_display,
+)
+from engine.pipeline.controller import PipelineRunner
+
+
+def test_figment_renders_in_pipeline():
+    """Verify figment renders overlay in pipeline."""
+    # Discover plugins
+    discover_plugins()
+
+    # Get figment plugin
+    registry = get_registry()
+    figment = registry.get("figment")
+
+    # Configure with short interval for testing
+    config = EffectConfig(
+        enabled=True,
+        intensity=1.0,
+        params={
+            "interval_secs": 0.1,  # 100ms
+            "display_secs": 1.0,
+            "figment_dir": "figments",
+        },
+    )
+    figment.configure(config)
+
+    # Create pipeline
+    pipeline = Pipeline(
+        config=PipelineConfig(
+            source="empty",
+            display="null",
+            camera="feed",
+            effects=["figment"],
+        )
+    )
+
+    # Add source stage
+    from engine.data_sources.sources import EmptyDataSource
+    from engine.pipeline.adapters import DataSourceStage
+
+    empty_source = EmptyDataSource(width=80, height=24)
+    pipeline.add_stage("source", DataSourceStage(empty_source, name="empty"))
+
+    # Add render stage
+    pipeline.add_stage("render", SourceItemsToBufferStage(name="items-to-buffer"))
+
+    # Add figment effect stage
+    pipeline.add_stage("effect_figment", EffectPluginStage(figment, name="figment"))
+
+    # Add display stage
+    from engine.display import DisplayRegistry
+
+    display = DisplayRegistry.create("null")
+    display.init(0, 0)
+    pipeline.add_stage("display", create_stage_from_display(display, "null"))
+
+    # Build and initialize pipeline
+    pipeline.build()
+    assert pipeline.initialize()
+
+    # Use PipelineRunner to step through frames
+    runner = PipelineRunner(pipeline)
+    runner.start()
+
+    # Run pipeline until figment renders (or timeout)
+    figment_rendered = False
+    for i in range(30):
+        runner.step()
+
+        # Check if figment rendered by inspecting the display's internal buffer
+        # The null display stores the last rendered buffer
+        if hasattr(display, "_last_buffer") and display._last_buffer:
+            buffer = display._last_buffer
+            # Check if buffer contains ANSI escape codes (indicating figment overlay)
+            # Figment adds overlay lines at the end of the buffer
+            for line in buffer:
+                if "\x1b[" in line:
+                    figment_rendered = True
+                    print(f"Figment rendered at frame {i}")
+                    # Print first few lines containing escape codes
+                    for j, line in enumerate(buffer[:10]):
+                        if "\x1b[" in line:
+                            print(f"Line {j}: {repr(line[:80])}")
+                    break
+            if figment_rendered:
+                break
+
+    assert figment_rendered, "Figment did not render in 30 frames"
+
+
+if __name__ == "__main__":
+    test_figment_renders_in_pipeline()
+    print("Test passed!")