Previously, the SHELL_SAFE_COMMAND_PATTERN was overly restrictive and blocked
legitimate characters needed for common Docker operations:
- Allow & for command chaining with && in multi-step build commands
- Allow " for build arguments with spaces (e.g., --build-arg KEY="value")
Update validation messages to reflect the new allowed operators and refactor
code to use imports instead of full class paths for better readability.
e2ba44d0c3