bannedCommands should be configurable/overridable

[gardner]

This discussion is for approval of changes outlined in #515

We've added two new configuration options to make the bash tool's command blocking more flexible:

1. banned_commands - Allows users to add additional commands to the default banned list
2. allowed_commands - Allows users to override any banned commands (including defaults)

Changes Made:

1. Added BannedCommands and AllowedCommands fields to the Options struct in config.go
2. Modified the bash tool in bash.go to:
   • Merge user-configured banned commands with defaults
   • Remove any allowed commands from the banned list
   • Maintain all existing functionality
3. Updated documentation in bash.md with examples of both configuration options
4. Added tests in bash_config_test.go to verify the behavior

Usage Example:

To allow curl and wget while maintaining other security restrictions, users can add this to
their Crush configuration:

{
  "options": {
   "allowed_commands": ["curl", "wget"]
  }
}

The implementation prioritizes allowed_commands over banned_commands, so if a command appears in both lists, it will be allowed.

Preview: https://github.com/charmbracelet/crush/compare/main...gardner:feature/configurable-banned-commands?expand=1

[gardner]

I don't do CLAs. Sorry for the noise!