Make llms.txt workflow idempotent for same-day reruns

Use checkout -B and force-with-lease push so the workflow can safely
rerun on the same day. Only create a PR if one doesn't already exist
for the branch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ctauchen

.github/workflows/generate-llms-txt.yml

@@ -57,14 +57,16 @@ jobs:
           BRANCH="chore/update-llms-txt-$(date +%Y-%m-%d)"
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
-          git checkout -b "$BRANCH"
+          git checkout -B "$BRANCH"
           git add static/llms.txt \
             static/calico/llms.txt static/calico/llms-full.txt \
             static/calico-enterprise/llms.txt static/calico-enterprise/llms-full.txt \
             static/calico-cloud/llms.txt static/calico-cloud/llms-full.txt
           git commit -m "chore: update generated llms.txt files"
-          git push -u origin "$BRANCH"
-          gh pr create \
-            --title "chore: update generated llms.txt files" \
-            --body "Automated weekly update of llms.txt and llms-full.txt files." \
-            --base main
+          git push --force-with-lease -u origin "$BRANCH"
+          if ! gh pr list --head "$BRANCH" --json number --jq '.[0].number' | grep -q .; then
+            gh pr create \
+              --title "chore: update generated llms.txt files" \
+              --body "Automated weekly update of llms.txt and llms-full.txt files." \
+              --base main
+          fi