Parse CLI boolean values explicitly

[xuu33030]

Summary

sqlformat --comma_first False currently enables comma-first formatting: argparse calls bool('False'), which is true. The same problem affects --compact; even xxx is silently accepted as true.

Keep the existing value-taking syntax and false defaults, but parse true/false case-insensitively and 1/0 explicitly. Reject other values with an argparse error. The help text now lists the accepted values, and the changelog records the behavior change. No formatter API or formatting algorithm changes.

Closes #638.

Validation

• Before the fix: 8 new false-value cases fail and 8 true-value controls pass.
• Full suite on macOS with CPython 3.10.20, 3.11.15, 3.12.14, 3.13.5 and 3.14.6: 540 passed, 2 xfailed, 1 xpassed on each version. The xfail/xpass results are also present on the unmodified baseline (506 passed, 2 xfailed, 1 xpassed on 3.12).
• Command: uv run --frozen --group dev --python <version> pytest tests/ -q.
• Tests cover valid values, defaults, invalid values, and actual python -m sqlparse subprocess output for both options.
• uv run --frozen --group dev ruff check sqlparse/ and git diff --check pass.
• Windows, Linux and PyPy were not run locally.

Checklist

• ran the tests (pytest)
• all style issues addressed (ruff)
• changes are covered by tests
• changes are documented (CLI help and changelog)

AI disclosure: Hermes Agent assisted with investigation, implementation, tests and this description under the submitting account owner's authorization. No independent human review is claimed.