Module shell_allowlist 

Shell allowlist with AST-based command parsing.

Security model (Information Bottleneck principle):

• When allowlist is set: ALL segments of a compound command must be allowed (deny-by-default)
• When empty: all commands pass (backwards-compatible blocklist-only mode)
• Dangerous patterns (subshells, eval, backticks) are blocked in restricted mode

Functions

check_shell_allowlist

Checks if a command is allowed by the shell allowlist. Returns Ok(()) if allowed, Err(message) if blocked.

extract_base_command