feat: add PR pipeline type detection workflow

- Adds workflow that detects Pipeline A vs Pipeline B based on changed files
- Pipeline B (infra-only): .github/, *.md, .eslintrc*, .prettierrc*, renovate.json*, .gitignore, .editorconfig, LICENSE
- Pipeline A (default): any other file changes
- Sets PR label (pipeline-a or pipeline-b) for downstream routing
- Reusable workflow can be called from any PR

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/detect-pr-pipeline.yaml

@@ -0,0 +1,73 @@
+name: Detect PR Pipeline Type
+
+on:
+  pull_request:
+    branches: [main, dev, uat]
+  workflow_call:
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  detect-pipeline:
+    runs-on: runners-privilegedescalation
+    timeout-minutes: 5
+    outputs:
+      pipeline-type: ${{ steps.detect.outputs.pipeline-type }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Get changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v44
+        with:
+          files_separator: '\n'
+
+      - name: Detect pipeline type
+        id: detect
+        run: |
+          echo "Changed files:"
+          echo "${{ steps.changed-files.outputs.all_changed_files }}"
+
+          pipeline="pipeline-a"
+
+          if [ -n "${{ steps.changed-files.outputs.all_changed_files }}" ]; then
+            all_infra=true
+            while IFS= read -r file; do
+              filename=$(basename "$file")
+              dirname=$(dirname "$file")
+
+              if [ "$dirname" = ".github" ] || \
+                 [[ "$filename" == *.md ]] || \
+                 [[ "$filename" == .eslintrc* ]] || \
+                 [[ "$filename" == .prettierrc* ]] || \
+                 [[ "$filename" == renovate.json* ]] || \
+                 [[ "$filename" == .gitignore ]] || \
+                 [[ "$filename" == .editorconfig ]] || \
+                 [[ "$filename" == LICENSE ]]; then
+                continue
+              else
+                all_infra=false
+                echo "Non-infra file found: $file"
+                break
+              fi
+            done <<< "${{ steps.changed-files.outputs.all_changed_files }}"
+
+            if [ "$all_infra" = true ]; then
+              pipeline="pipeline-b"
+            fi
+          fi
+
+          echo "pipeline-type=$pipeline" >> $GITHUB_OUTPUT
+          echo "Detected pipeline: $pipeline"
+
+      - name: Set PR label
+        if: github.event_name == 'pull_request'
+        run: |
+          gh pr edit "${{ github.event.pull_request.number }}" \
+            --add-label "${{ steps.detect.outputs.pipeline-type }}"