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_pipeline.py

@@ -0,0 +1,79 @@
+"""
+Integration tests for figment effect in the pipeline.
+"""
+
+from engine.effects.plugins import discover_plugins
+from engine.effects.registry import get_registry
+from engine.pipeline import Pipeline, PipelineConfig, get_preset
+from engine.pipeline.adapters import (
+    EffectPluginStage,
+    SourceItemsToBufferStage,
+    create_stage_from_display,
+)
+from engine.pipeline.controller import PipelineRunner
+
+
+class TestFigmentPipeline:
+    """Tests for figment effect in pipeline integration."""
+
+    def setup_method(self):
+        """Discover plugins before each test."""
+        discover_plugins()
+
+    def test_figment_in_pipeline(self):
+        """Figment effect can be added to pipeline."""
+        registry = get_registry()
+        figment = registry.get("figment")
+
+        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 for a few frames
+        for i in range(10):
+            runner.step()
+            # Result might be None for null display, but that's okay
+
+        # Verify pipeline ran without errors
+        assert pipeline.context.params.frame_number == 10
+
+    def test_figment_preset(self):
+        """Figment preset is properly configured."""
+        preset = get_preset("test-figment")
+        assert preset is not None
+        assert preset.source == "empty"
+        assert preset.display == "terminal"
+        assert "figment" in preset.effects