Add CI workflow to validate agentic workflow compilation

Adds validate-agentic-workflows.yml that runs on PRs touching workflows/.
Uses gh-aw CLI setup action to install the compiler, then runs
'gh aw compile --validate' on each workflow .md file. Posts a sticky
PR comment with fix instructions on failure.

Also adds workflows/** to validate-readme.yml path triggers so README
tables are regenerated when workflows change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/validate-agentic-workflows.yml

@@ -0,0 +1,73 @@
+name: Validate Agentic Workflows
+
+on:
+  pull_request:
+    branches: [staged]
+    types: [opened, synchronize, reopened]
+    paths:
+      - "workflows/**"
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  validate-workflows:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install gh-aw CLI
+        uses: github/gh-aw/actions/setup-cli@main
+
+      - name: Find and compile workflow files
+        id: compile
+        run: |
+          exit_code=0
+          found=0
+
+          # Find all .md files in workflows/ subfolders (excluding README.md)
+          for workflow_file in workflows/*/*.md; do
+            [ -f "$workflow_file" ] || continue
+            basename=$(basename "$workflow_file")
+            [ "$basename" = "README.md" ] && continue
+
+            found=$((found + 1))
+            echo "::group::Compiling $workflow_file"
+            if gh aw compile --validate "$workflow_file"; then
+              echo "✅ $workflow_file compiled successfully"
+            else
+              echo "❌ $workflow_file failed to compile"
+              exit_code=1
+            fi
+            echo "::endgroup::"
+          done
+
+          if [ "$found" -eq 0 ]; then
+            echo "No workflow .md files found to validate (README.md files are excluded)."
+          else
+            echo "Validated $found workflow file(s)."
+          fi
+
+          echo "status=$( [ $exit_code -eq 0 ] && echo success || echo failure )" >> "$GITHUB_OUTPUT"
+          exit $exit_code
+
+      - name: Comment on PR if compilation failed
+        if: failure()
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          header: workflow-validation
+          message: |
+            ## ❌ Agentic Workflow compilation failed
+
+            One or more workflow files in `workflows/` failed to compile with `gh aw compile --validate`.
+
+            Please fix the errors and push again. You can test locally with:
+
+            ```bash
+            gh extension install github/gh-aw
+            gh aw compile --validate <your-workflow-file>.md
+            ```
+
+            See the [Agentic Workflows documentation](https://github.github.com/gh-aw) for help.

.github/workflows/validate-readme.yml

@@ -9,6 +9,7 @@ on:
       - "prompts/**"
       - "agents/**"
       - "plugins/**"
+      - "workflows/**"
       - "*.js"
       - "README.md"
       - "docs/**"