Add concurrency cancel and ignore docs/markdown changes across CI workflows (#168)

* Add concurrency cancel and ignore docs/markdown changes across CI workflows

* Clarify PR-only concurrency (no push queuing)

.github/workflows/pmg-e2e.yml

@@ -4,11 +4,22 @@ on:
   pull_request:
     branches:
       - main
+    paths-ignore:
+      - "**/*.md"
+      - "docs/**"
   push:
     branches:
       - main
+    paths-ignore:
+      - "**/*.md"
+      - "docs/**"
   workflow_dispatch:
 
+# PRs share a concurrency group (cancel/serialize); Pushes use unique groups to avoid cancellation/queuing
+concurrency:
+  group: ${{ github.workflow }}-${{ (github.event_name == 'pull_request' && github.ref) || github.run_id }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 permissions:
   contents: read