feat: gate gitea_delete_branch on gitea.branch.delete capability (Closes #408)

Add fail-closed profile gate at tool entry before preflight or API calls,
return structured permission reports on block, and record required_permission
in delete_branch audit metadata. Regression tests prove resolver-denied
sessions cannot bypass the gate through the raw tool.

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

gitea_mcp_server.py

@@ -3463,16 +3463,32 @@ def gitea_delete_branch(
         repo: Override the repository name.
 
     Returns:
-        dict with 'success' and 'message'.
+        dict with 'success' and 'message'; on a permission block,
+        'success'/'performed' False, 'reasons', and a structured
+        'permission_report' (#142) with no API call made.
     """
+    gate_reasons = _profile_operation_gate("gitea.branch.delete")
+    if gate_reasons:
+        return {
+            "success": False,
+            "performed": False,
+            "required_permission": "gitea.branch.delete",
+            "reasons": gate_reasons,
+            "permission_report": _permission_block_report("gitea.branch.delete"),
+        }
+
     verify_preflight_purity(remote)
     h, o, r = _resolve(remote, host, org, repo)
     auth = _auth(h)
     import urllib.parse
     encoded_branch = urllib.parse.quote(branch, safe="")
     url = f"{repo_api_url(h, o, r)}/branches/{encoded_branch}"
+    request_metadata = {
+        "branch": branch,
+        "required_permission": "gitea.branch.delete",
+    }
     with _audited("delete_branch", host=h, remote=remote, org=o, repo=r,
-                  target_branch=branch, request_metadata={"branch": branch}):
+                  target_branch=branch, request_metadata=request_metadata):
         api_request("DELETE", url, auth)
     return {"success": True, "message": f"Remote branch '{branch}' deleted."}