BashTool input validation security hardening

[RinZ27]

The BashTool currently allows some potentially unsafe shell syntax to pass through command parsing. We need to harden the input validation to prevent command injection and ensure a safer execution environment.

Specific improvements needed:

• Validate command names against invalid characters.
• Detect and block dangerous shell syntax like pipelines and redirections during parsing.
• Ensure the execution environment is sane.