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).

presets.toml

@@ -40,6 +40,15 @@ camera_speed = 0.5
 viewport_width = 80
 viewport_height = 24
 
+[presets.test-figment]
+description = "Test: Figment overlay effect"
+source = "empty"
+display = "terminal"
+camera = "feed"
+effects = ["figment"]
+viewport_width = 80
+viewport_height = 24
+
 # ============================================
 # DEMO PRESETS (for demonstration and exploration)
 # ============================================