fix(ralph-wiggum): Fix cancel-ralph command parsing error

[Adoom666]

The cancel-ralph command was failing with a bash parse error because the inline multi-line bash code in the ```! code block was being passed to bash with the fence markers included.

This fix:

1. Creates a dedicated cancel-ralph-loop.sh script in scripts/
2. Updates cancel-ralph.md to call the script via allowed-tools pattern
3. Matches the working pattern used by ralph-loop.md

The script properly handles both cases:

• Active loop: removes state file, reports iteration count
• No loop: reports "No active Ralph loop found"

Tested successfully on macOS.