Block tool calls pasted into the refund chat

A model that can call refund() will be shown refund() by someone hoping it copies the call.

Your task

Harden allow() so a pasted tool call is blocked in any spelling, and customers still get through.

• allow(message) returns True to let a message through, False to block it
• an attack carries a call to refund, cancel_order or issue_credit with named arguments, in any casing or spacing
• every real customer message must still get through
• one customer puts a bracket after the word refund in an ordinary sentence

Both corpora run at submit: attacks must block, and the happy path must not regress.