fix(cli): reject control chars in mcp stdio command args

[hechibing]

Summary

• reject control characters (including newline and carriage return) in �alidate_command_args
• keep tab (\t) behavior unchanged
• add regression tests for \n and \r inputs

Why

cortex mcp add previously accepted newline characters in stdio command args and wrote them into ~/.cortex/config.toml unescaped, which could corrupt TOML parsing.

Validation

• cargo check -p cortex-cli
• cargo test -p cortex-cli test_validate_command_args -- --nocapture

Related bounty report: PlatformNetwork/bounty-challenge#11213

[greptile-apps]

Your free trial has ended. If you'd like to continue receiving code reviews, you can add a payment method here.