Added workflow to auto-tag docs PRs based on distro sync PRs.

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,6 +7,7 @@
 | Info | Please fill out this column |
 | ------ | ----------- |
 | Ticket(s) this addresses   | (add tickets here #1) |
+| Documentation | (link to docs PR, pending, or N/A) | <!-- New features, parameter changes, and default value changes must be documented -->
 | Primary OS tested on | (Ubuntu, MacOS, Windows) |
 | Robotic platform tested on | (Steve's Robot, gazebo simulation of Tally, hardware turtlebot) |
 | Does this PR contain AI generated software? | (No; Yes and it is marked inline in the code) |

.github/workflows/autotag_docs.yml

@@ -0,0 +1,45 @@
+name: Label docs PRs for backports
+on:
+  pull_request:
+    branches:
+      - humble
+      - jazzy
+      - kilted
+
+jobs:
+  label-docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Process docs PRs
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Get PR numbers from commits
+          prs=$(gh api repos/ros-navigation/navigation2/pulls/${{ github.event.number }}/commits \
+            --jq '.[].commit.message' | grep -o '#[0-9]\+' | tr -d '#' | sort -u)
+
+          # Find and label docs PRs
+          docs_pr_found=false
+          label="backport-${{ github.event.pull_request.base.ref }}"
+
+          for pr in $prs; do
+
+            # Get cross-referenced events
+            docs_pr=$(gh api repos/ros-navigation/navigation2/issues/$pr/timeline \
+              --jq '.[] | select(.event == "cross-referenced" and .source.issue.repository.name == "docs.nav2.org") | .source.issue.number' \
+              2>/dev/null | head -1)
+
+            if [ -n "$docs_pr" ]; then
+              echo "Labeling docs PR #$docs_pr with '$label'"
+              gh pr edit $docs_pr --repo ros-navigation/docs.nav2.org --add-label "$label"
+              docs_pr_found=true
+            else
+              echo "No cross-referenced docs PR found for navigation2 PR #$pr"
+            fi
+          done
+
+          # Fail if no docs PRs were found
+          if [ "$docs_pr_found" = false ]; then
+            echo "ERROR: No docs PRs found for this backport"
+            exit 1
+          fi