Block author mutations from reviewer MCP namespace (Issue #209)

Add role_namespace_gate to fail closed when reviewer-bound sessions attempt
author mutations (create_pr always blocked; create_issue only when profile
explicitly grants gitea.issue.create). Extend mutation audit records with
mcp_namespace, task_role, and operation fields. Add handoff parity checks in
review_proofs for author role vs reviewer namespace mismatches.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

gitea_audit.py

@@ -163,12 +163,13 @@ def audit_enabled():
 def build_event(*, action, result, remote=None, server=None, repository=None,
                 issue_number=None, pr_number=None, profile_name=None,
                 audit_label=None, authenticated_username=None, target_branch=None,
-                head_sha=None, reason=None, request_metadata=None, now=None):
+                head_sha=None, reason=None, request_metadata=None, now=None,
+                mcp_namespace=None, task_role=None, operation=None):
     """Build a redacted, JSON-able audit record for a mutating action."""
     ts = now or datetime.datetime.now(datetime.timezone.utc)
     if isinstance(ts, datetime.datetime):
         ts = ts.isoformat()
-    return {
+    event = {
         "timestamp": ts,
         "action": action,
         "action_type": "mutating",
@@ -186,6 +187,13 @@ def build_event(*, action, result, remote=None, server=None, repository=None,
         "reason": _redact_str(reason) if reason else reason,
         "request_metadata": redact(request_metadata) if request_metadata is not None else None,
     }
+    if mcp_namespace is not None:
+        event["mcp_namespace"] = mcp_namespace
+    if task_role is not None:
+        event["task_role"] = task_role
+    if operation is not None:
+        event["operation"] = operation
+    return event
 
 
 def write_event(event, path=None):