test: keep webui CI hermetic offline

webui/lease_loader.py

@@ -228,10 +228,29 @@ def load_lease_snapshot(
         )
 
     host = _host_from_url(project.remote_host)
-    pr_fetch = fetch_prs or _fetch_prs
-    issue_fetch = fetch_issues or _fetch_issues
-    comment_fetch = fetch_comments or _fetch_comments
-    using_live = fetch_prs is None or fetch_issues is None
+    offline_test = (os.environ.get("WEBUI_TEST_OFFLINE") or "").strip() in {
+        "1",
+        "true",
+        "yes",
+    }
+
+    def _empty_pr_fetch(*_args, **_kwargs):
+        return [], None
+
+    def _empty_issue_fetch(*_args, **_kwargs):
+        return [], None
+
+    def _empty_comment_fetch(*_args, **_kwargs):
+        return []
+
+    pr_fetch = fetch_prs or (_empty_pr_fetch if offline_test else _fetch_prs)
+    issue_fetch = fetch_issues or (
+        _empty_issue_fetch if offline_test else _fetch_issues
+    )
+    comment_fetch = fetch_comments or (
+        _empty_comment_fetch if offline_test else _fetch_comments
+    )
+    using_live = not offline_test and (fetch_prs is None or fetch_issues is None)
     auth = get_auth_header(host) if using_live else "test-auth"
 
     if using_live and not auth:
@@ -328,4 +347,4 @@ def snapshot_to_dict(snapshot: LeaseSnapshot) -> dict[str, Any]:
         ],
         "collision_history": list(snapshot.collision_history),
         "fetch_error": snapshot.fetch_error,
-    }
+    }