[johnthagen]

Closes #69

• Support Python 3.15
• Drop EOL Python 3.10
• Add explicit TypeAlias where needed to prepare for type syntax in Python 3.12+
• Update all dependencies

Several updates are to deal with coverage 7 subprocess changes:

env={**os.environ, "UV_PROJECT_ENVIRONMENT": str(TESTING_FOLDER / ".venv")}

[tool.coverage]
# pytest-cov 7 delegates subprocess measurement to coverage.py.
run.patch = [ "subprocess" ]