ci: add automated check for help output consistency with README

[Copilot]

Adds a CI check that validates the help output in README.md matches uv run gimmegit -h to prevent documentation drift.

Changes

• scripts/check_help_consistency.py: Extracts help text from README.md's "# Command reference" section and compares against live gimmegit -h output. Exits with detailed diff on mismatch.

• .github/workflows/checks.yaml: Added "Check help consistency" step after unit tests, runs via uv run python for dependency consistency.

The check will catch any future changes to _help.py that aren't reflected in README.md.

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• astral.sh
  • Triggering command: /usr/bin/curl curl -LsSf REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)