Woodpecker gRPC agent_id metadata can be spoofed- cross-tenant agent impersonation

Woodpecker is a CI/CD engine. Starting in version 3.0.0 and prior to version 3.14.1, a vulnerability in Woodpecker CI's gRPC layer allowed any authenticated agent to impersonate any other agent on the same server by injecting a forged `agent_id` value into outgoing gRPC metadata. The server correctly verified the JWT token but then discarded the verified agent identity in favor of the client-supplied value. Version 3.14.1 patches the issue. As a workaround, disable org agents (`WOODPECKER_DISABLE_USER_AGENT_REGISTRATION=true`) and delete existing ones.