feat(cli): categorize /help into General/Model/Session/Git groups

[aryansk]

Summary

Closes #31 — groups the /help slash-command listing into General, Model, Session, and Git categories so the growing command set stays scannable.

Changes

• gcode/cli.py — _print_help now emits categorized group headers with Rich markup (rendered by the existing RichUI.info → console.print path); no command was dropped or reworded.
• tests/test_cli.py — regression test asserting all four category headers plus a representative command per group appear in the help text.

Why

The flat command list has grown past a dozen entries; grouping by usage area makes discovery faster without changing any command behavior.

Validation

• pytest: 26/26 pass
• ruff check + ruff format --check: clean
• mypy + bandit: clean

[shauryagangrade]

Review

Nice, tight change — all 12 commands preserved, Rich markup renders correctly (verified via a real console.print), 26/26 tests pass, ruff/mypy/bandit clean. The new test covers all four group headers plus a representative command each.

Two docs items to close before merge:

1. Demo snapshot (stale): demo/make_demo.py:229-237 hardcodes the old flat /help output — the recorded demo will disagree with real output after this lands. Repo convention keeps it in sync (e.g. commit 9e39fbe). Please update it, and check demo/demo.tape regenerates cleanly.
2. CHANGELOG (missing): this is a user-visible feature — add an entry under CHANGELOG.md Unreleased > Added.

Minor nit: /setup under "Session" is defensible but could equally be "Model"; fine either way.

[shauryagangrade]

Merged. Thanks for your work here.

If you would like to contribute to more repos just like this, I recommend:

https://github.com/shauryagangrade/intent-drift-skill
https://github.com/shauryagangrade/scout-issue
https://github.com/StudentSuite/StudyMap
https://github.com/shauryagangrade/GCode
https://github.com/shauryagangrade/intent-drift

[aryansk]

Thanks for the review and for merging this. Both docs items are noted and remain outstanding on the merged tree: the demo/make_demo.py snapshot still hardcodes the old flat /help output, and CHANGELOG.md Unreleased has no entry for the categorized help (nor one for the non-interactive execute_bash fix in #43). I'll submit a small follow-up PR that adds both CHANGELOG entries and refreshes the demo snapshot so the recorded output matches the current command output.