[Feature] Tool-level RBAC — role-based access control per agent tool

[mosw]

Body:
Add the ability to define role-based permissions at the tool level. Different agents or users should have different security policies.
pythonpolicies = {
"analyst_agent": {
"sql": {"allowed": ["SELECT"], "pii_redaction": True},
"file": {"allowed": ["read"]}
},
"admin_agent": {
"sql": {"allowed": ["SELECT", "INSERT", "UPDATE", "DELETE"], "require_where": True},
"file": {"allowed": ["read", "write"]}
}
}
This enables least-privilege enforcement per agent — critical for multi-agent production systems.