docs: add CHANGELOG entries for #43/#44 and sync demo /help snapshot

[aryansk]

Problem

Follow-up to the review comments on the two GCode PRs merged today:

• #44 — the review asked
  for demo/make_demo.py to stop hardcoding the old flat /help snapshot and
  instead mirror the categorized /help output.

Change

• demo/make_demo.py: the /help demo block now mirrors the categorized
  output from _print_help in gcode/cli.py, including /ollama, /pull,
  /setup, and /diff, which were missing from the flat snapshot, plus the
  "Any other input is sent to the agent." line.

This branch intentionally touches only demo/make_demo.py — the CHANGELOG
entries for #43/#44 already landed on main at merge time.

Why this approach

Keeps the recorded demo in sync with the real /help output. Note the demo
pipeline has since migrated to vhs (vhs demo/demo.tape → docs/demo.gif,
documented in the README's "Demo GIF" section); make_demo.py is a legacy
self-contained renderer kept because it reproduces the exact Rich markup of
_print_help, and its docstring now says so.

Testing

uv run python -m compileall -q gcode demo      # OK
uv run ruff check .                            # All checks passed

The demo /help markup was rendered through Rich to confirm it parses and
produces the categorized layout (verified by the maintainer).

Documentation and release impact

• User-facing documentation updated (demo script)
• Changelog/release note needed (already on main from fix(tools): make execute_bash non-interactive-safe #43/feat(cli): categorize /help into General/Model/Session/Git groups #44)
• Migration or compatibility note needed
• No documentation impact

[shauryagangrade]

Thanks for the follow-up! Most of this already landed on main, so this PR now conflicts and should be slimmed down. Verified against current main:

1. The CHANGELOG half is redundant — please drop it.
Both entries already exist on main (added at merge time):

• CHANGELOG.md → Unreleased > Changed: "/help command listing grouped by category (General, Model, Session, Git)…"
• CHANGELOG.md → Unreleased > Fixed: "execute_bash no longer hangs or crashes when its approval prompt runs in a non-interactive environment…"

A rebase onto main fails with a conflict in CHANGELOG.md for exactly this reason. Keep only the demo/make_demo.py change.

2. The make_demo.py change is still useful, but conflicts too.
main already has a partial categorized /help snapshot (commit 3e2df7f) that's missing /ollama, /pull, /setup, /diff, and the "Any other input is sent to the agent." line. Your version completes it and matches _print_help exactly — I rendered it through Rich and it parses cleanly. After rebasing, resolve the conflict by keeping your full version.

3. Stale premises in the description (worth updating).

• demo/demo.tape is no longer an asciinema recording: the demo pipeline was migrated to vhs (vhs demo/demo.tape → docs/demo.gif, documented in the README's new "Demo GIF" section). It can now be regenerated headless.
• make_demo.py is legacy after that migration, and its docstring still claims it outputs docs/demo.gif — which is now vhs-generated. Consider updating the docstring or dropping the script.

[aryansk]

Thanks for the detailed review — all three points addressed:

1. CHANGELOG dropped. The branch now touches only demo/make_demo.py.
2. make_demo.py kept in full. Rebased onto current main and resolved the
   conflict by keeping the complete /help snapshot (/ollama, /pull,
   /setup, /diff, and the "Any other input is sent to the agent." line).
3. Description updated and the script docstring now notes the vhs migration
   (vhs demo/demo.tape → docs/demo.gif) and that this renderer is kept for
   verifying /help snapshot changes against the exact Rich markup.

Branch now merges cleanly against main.