- Add DataType enum (SOURCE_ITEMS, TEXT_BUFFER, etc.)
- Add inlet_types and outlet_types to Stage
- Add _validate_types() for type checking at build time
- Update tests with proper type annotations
- Add TransformDataSource for filtering/mapping source items
- Add MetricsDataSource for rendering live pipeline metrics as ASCII art
- Fix display stage registration in StageRegistry
- Register sources with both class name and simple name aliases
- Fix DisplayStage.init() to pass reuse parameter
- Simplify create_default_pipeline to use DataSourceStage wrapper
- Set pygame as default display
- Remove old pipeline tasks from mise.toml
- Add tests for new pipeline architecture
