Add gate.cat to agent firewalls and gateways

[BGMLAI]

Summary

Adds gate.cat to Agent Firewalls & Gateways (Runtime Protection).

It is an Apache-2.0, actively maintained, local deterministic veto that runs before coding-agent actions and blocks named destructive command classes. The entry follows the repository's requested one-line format and makes no performance or adoption claims.

Disclosure: I maintain gate.cat.

Checks

• Searched the current list; gate.cat is not already present.
• Repository is public and active: https://github.com/BGMLAI/gate.cat
• Link returns HTTP 200.
• git diff --check passes.

[BGMLAI]

Closing as a duplicate of #73 — both add gate.cat to the same Agent Firewalls & Gateways section. Consolidating to a single PR to keep things clean; #73 has the fuller description (it also notes the identity/billing/secret-exfiltration command classes). Thanks for curating this list.