chore: ci matrix, documentation updates, and version bump to 0.6.0

[torrua]

Summary of Changes

Stage 4: CI Matrix, Documentation Polish, and Release Version Bump

• Point 2 (CI Matrix):
  • Expanded Python version matrix in .github/workflows/pytest.yml to test across ["3.10", "3.11", "3.12", "3.13"].
• Point 3 (Docstring Typos):
  • Fixed typo in loglan_core/event.py (dateime.date -> datetime.date).
  • Fixed typo in loglan_core/setting.py (dateime.datetime -> datetime.datetime).
• Point 4 (Documentation & Examples):
  • Updated examples/word.md and examples/word_selector.md to demonstrate modern .statement usage, session.scalars(...), synchronous and asynchronous session methods, and clarified word.keys and hybrid derivative properties (word.affixes, word.complexes).
• Point 5 (Version & Package Metadata):
  • Bumped version in pyproject.toml and loglan_core/__init__.py to 0.6.0.
  • Added Programming Language :: Python :: 3.13 classifier and updated download URL.

Verification

• 198 pytest tests passing (sync and async).
• 10.00/10 Pylint score on loglan_core.
• 100% Black formatting compliance.
• Strict Mypy typecheck 0 errors.