fix(skills): agent-created skills were incorrectly treated as untrusted community content

_resolve_trust_level() didn't handle 'agent-created' source, so it
fell through to 'community' trust level. Community policy blocks on
any caution or dangerous findings, which meant common patterns like
curl with env vars, systemctl, crontab, cloudflared references etc.
would block skill creation/patching.

The agent-created policy row already existed in INSTALL_POLICY with
permissive settings (allow caution, ask on dangerous) but was never
reached. Now it is.

Fixes reports of skill_manage being blocked by security scanner.

tools/skills_guard.py

@@ -1050,6 +1050,9 @@ def _get_configured_model() -> str:
 
 def _resolve_trust_level(source: str) -> str:
     """Map a source identifier to a trust level."""
+    # Agent-created skills get their own permissive trust level
+    if source == "agent-created":
+        return "agent-created"
     # Official optional skills shipped with the repo
     if source.startswith("official/") or source == "official":
         return "builtin"