feat: Add --version / -v flag to taintline CLI (#13)

[IronLad123]

Closes #13

Summary of Changes

• Added -v / --version flag to taintline CLI in src/taintline/cli.py utilizing importlib.metadata.version('taintline') with fallback to taintline.__version__.
• Integrated seamlessly with the subcommand parser without affecting taintline check ... or future subcommands.
• Added unit test assertions in tests/test_smoke.py verifying exit code 0 and version string output for both --version and -v flags.

Verification

• pytest: 47 passed in 1.14s.
• mypy src: Success: no issues found in 8 source files (strict mode).
• ruff check src tests: All checks passed!.

[bamdadd]

Merged! 🎉 Landed on main as 36417e6, with you as the author.

Thank you so much — and a special welcome, since this is your first contribution here. This was a genuinely clean PR: you wired --version to the installed package metadata via importlib.metadata.version('taintline') (exactly the single-source-of-truth approach we'd want, no hardcoded string on the happy path), added tests covering both --version and -v with exit-code and output assertions, and kept ruff/mypy-strict/pytest all green. It also correctly stays clear of the deterministic check path.

This closes #13. Hope to see more from you — there are a few good-first-issues open if you're looking for the next one, and I'm happy to help you get started on any of them. Thanks again for making taintline a little better. 🙏

[IronLad123]

Thank you so much for the warm welcome and thoughtful feedback @bamdadd! I'm really glad the implementation and test coverage met the repository's standards. I look forward to contributing more to taintline and the rest of the ecosystem!