ci: auto-fill PR metadata

Author: Seungpyo1007

.github/workflows/pr-metadata.yml

@@ -0,0 +1,60 @@
+name: pr-metadata
+
+# Keep PR triage fields useful without requiring manual cleanup on every branch.
+# This workflow only updates PR metadata; it never checks out or executes PR code.
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize, ready_for_review]
+
+permissions:
+  contents: read
+  issues: write
+  pull-requests: read
+
+jobs:
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Assign author and label by changed paths
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pr = context.payload.pull_request;
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+            const issue_number = pr.number;
+
+            if (!pr.user?.type?.endsWith('Bot')) {
+              await github.rest.issues.addAssignees({
+                owner,
+                repo,
+                issue_number,
+                assignees: [pr.user.login],
+              });
+            }
+
+            const files = await github.paginate(github.rest.pulls.listFiles, {
+              owner,
+              repo,
+              pull_number: issue_number,
+              per_page: 100,
+            });
+
+            const labels = new Set();
+            for (const file of files) {
+              const path = file.filename;
+              if (path.startsWith('site/')) labels.add('site');
+              if (path.startsWith('data/') || path.startsWith('site/public/v1/') || path === 'site/public/openapi.json') labels.add('data');
+              if (path.startsWith('app/')) labels.add('app');
+              if (path.startsWith('.github/workflows/')) labels.add('ci');
+              if (path.startsWith('docs/') || path === 'README.md' || path.endsWith('.md')) labels.add('documentation');
+            }
+
+            if (labels.size) {
+              await github.rest.issues.addLabels({
+                owner,
+                repo,
+                issue_number,
+                labels: [...labels],
+              });
+            }