Expands the hardcoded security rules that block dangerous `rm` commands
in the agent terminal tool.
### New blocked patterns
- `rm -rf $HOME` / `rm -rf $HOME/` / `rm -rf ${HOME}` / `rm -rf
${HOME}/`
- `rm -rf .` / `rm -rf ./`
- `rm -rf ..` / `rm -rf ../`
- `rm -rf ~/` (previously only `rm -rf ~` was blocked)
### Flag handling improvements
- Simplified the flag character class from `[rRfF]` to `[rf]` since the
regex is already compiled with case-insensitive mode — less confusing,
same behavior.
- Added tests verifying that reversed flags (`-fr`), uppercase (`RM
-RF`), split flags (`-r -f`), and chained commands all get caught.
### Safe commands still allowed
Paths like `rm -rf ./build`, `rm -rf ~/Documents`, `rm -rf
$HOME/Documents`, `rm -rf ../some_dir`, and `rm -rf .hidden_dir` are
**not** blocked.
Release Notes:
- Auto-block a wider range of agent terminal commands, e.g. `rm -rf
$HOME` in addition to `rm -rf ~`