feat(pipeline): add unified pipeline architecture with Stage abstraction

- Add engine/pipeline/ module with Stage ABC, PipelineContext, PipelineParams
- Stage provides unified interface for sources, effects, displays, cameras
- Pipeline class handles DAG-based execution with dependency resolution
- PipelinePreset for pre-configured pipelines (demo, poetry, pipeline, etc.)
- Add PipelineParams as params layer for animation-driven config
- Add StageRegistry for unified stage registration
- Add sources_v2.py with DataSource.is_dynamic property
- Add animation.py with Preset and AnimationController
- Skip ntfy integration tests by default (require -m integration)
- Skip e2e tests by default (require -m e2e)
- Update pipeline.py with comprehensive introspection methods

engine/pipeline/__init__.py

@@ -0,0 +1,107 @@
+"""
+Unified Pipeline Architecture.
+
+This module provides a clean, dependency-managed pipeline system:
+- Stage: Base class for all pipeline components
+- Pipeline: DAG-based execution orchestrator
+- PipelineParams: Runtime configuration for animation
+- PipelinePreset: Pre-configured pipeline configurations
+- StageRegistry: Unified registration for all stage types
+
+The pipeline architecture supports:
+- Sources: Data providers (headlines, poetry, pipeline viz)
+- Effects: Post-processors (noise, fade, glitch, hud)
+- Displays: Output backends (terminal, pygame, websocket)
+- Cameras: Viewport controllers (vertical, horizontal, omni)
+
+Example:
+    from engine.pipeline import Pipeline, PipelineConfig, StageRegistry
+
+    pipeline = Pipeline(PipelineConfig(source="headlines", display="terminal"))
+    pipeline.add_stage("source", StageRegistry.create("source", "headlines"))
+    pipeline.add_stage("display", StageRegistry.create("display", "terminal"))
+    pipeline.build().initialize()
+
+    result = pipeline.execute(initial_data)
+"""
+
+from engine.pipeline.controller import (
+    Pipeline,
+    PipelineConfig,
+    PipelineRunner,
+    create_default_pipeline,
+    create_pipeline_from_params,
+)
+from engine.pipeline.core import (
+    PipelineContext,
+    Stage,
+    StageConfig,
+    StageError,
+    StageResult,
+)
+from engine.pipeline.params import (
+    DEFAULT_HEADLINE_PARAMS,
+    DEFAULT_PIPELINE_PARAMS,
+    DEFAULT_PYGAME_PARAMS,
+    PipelineParams,
+)
+from engine.pipeline.presets import (
+    DEMO_PRESET,
+    FIREHOSE_PRESET,
+    PIPELINE_VIZ_PRESET,
+    POETRY_PRESET,
+    PRESETS,
+    SIXEL_PRESET,
+    WEBSOCKET_PRESET,
+    PipelinePreset,
+    create_preset_from_params,
+    get_preset,
+    list_presets,
+)
+from engine.pipeline.registry import (
+    StageRegistry,
+    discover_stages,
+    register_camera,
+    register_display,
+    register_effect,
+    register_source,
+)
+
+__all__ = [
+    # Core
+    "Stage",
+    "StageConfig",
+    "StageError",
+    "StageResult",
+    "PipelineContext",
+    # Controller
+    "Pipeline",
+    "PipelineConfig",
+    "PipelineRunner",
+    "create_default_pipeline",
+    "create_pipeline_from_params",
+    # Params
+    "PipelineParams",
+    "DEFAULT_HEADLINE_PARAMS",
+    "DEFAULT_PIPELINE_PARAMS",
+    "DEFAULT_PYGAME_PARAMS",
+    # Presets
+    "PipelinePreset",
+    "PRESETS",
+    "DEMO_PRESET",
+    "POETRY_PRESET",
+    "PIPELINE_VIZ_PRESET",
+    "WEBSOCKET_PRESET",
+    "SIXEL_PRESET",
+    "FIREHOSE_PRESET",
+    "get_preset",
+    "list_presets",
+    "create_preset_from_params",
+    # Registry
+    "StageRegistry",
+    "discover_stages",
+    "register_source",
+    "register_effect",
+    "register_display",
+    "register_camera",
+]