CI: close PRs with excessive labels

.github/workflows/auto-response.yml

@@ -105,6 +105,26 @@ jobs:
               }
             }
 
+            const pullRequest = context.payload.pull_request;
+            if (pullRequest) {
+              const labelCount = pullRequest.labels?.length ?? 0;
+              if (labelCount > 20) {
+                await github.rest.issues.createComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: pullRequest.number,
+                  body: "Closing this PR because it has more than 20 labels, which usually means the branch is too noisy. Please recreate the PR from a clean branch.",
+                });
+                await github.rest.issues.update({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: pullRequest.number,
+                  state: "closed",
+                });
+                return;
+              }
+            }
+
             const labelName = context.payload.label?.name;
             if (!labelName) {
               return;