ci: annotate uv bump workflow with PR links (#39112)

When the uv pin bump workflow opens a PR (or finds one already open),
the Actions run now shows a notice annotation with the PR URL.

---

Previously the URL only appeared buried in step stdout after `gh pr
create`, which made it easy to miss from the run page. This matches the
same change in deepagents.

.github/workflows/bump_uv_pin.yml

@@ -75,10 +75,13 @@ jobs:
           BRANCH: ${{ steps.versions.outputs.branch }}
         run: |
           set -euo pipefail
-          count=$(gh pr list --head "$BRANCH" --state open --json number --jq 'length')
+          existing_json=$(gh pr list --head "$BRANCH" --state open --json number,url)
+          count=$(printf '%s' "$existing_json" | jq 'length')
           echo "count=$count" >> "$GITHUB_OUTPUT"
           if [ "$count" -gt 0 ]; then
+            pr_url=$(printf '%s' "$existing_json" | jq -r '.[0].url')
             echo "Open PR already exists for $BRANCH; skipping."
+            echo "::notice::Open uv bump PR already exists: $pr_url"
           fi
 
       - name: Wait for astral mirror to replicate
@@ -198,8 +201,10 @@ jobs:
             printf 'Opened automatically by `bump_uv_pin.yml`. Mirror availability on `releases.astral.sh` was verified before this PR was created, so CI should not race the fallback.\n'
           } > "$body_file"
 
-          gh pr create \
+          pr_url=$(gh pr create \
             --head "$BRANCH" \
             --base "$DEFAULT_BRANCH" \
             --title "chore(deps): bump uv to $LATEST" \
-            --body-file "$body_file"
+            --body-file "$body_file")
+          echo "Opened uv bump PR: $pr_url"
+          echo "::notice::Opened uv bump PR: $pr_url"