Add typed dataclasses for tuple returns:
- types.py: HeadlineItem, FetchResult, Block dataclasses with legacy tuple converters
- fetch.py: Add type hints and HeadlineTuple type alias
Add pyright for static type checking:
- Add pyright to dependencies
- Verify type coverage with pyright (0 errors in core modules)
This enables:
- Named types instead of raw tuples (better IDE support, self-documenting)
- Type-safe APIs across modules
- Backward compatibility via to_tuple/from_tuple methods
Note: Lazy imports skipped for render.py - startup impact is minimal.
