Improve GitHub Actions test pipeline

- Make YAML validation failures fail the build (removed continue-on-error)
- Split flake8 into syntax errors (fails) and style warnings (continues)
- Add concurrency control to cancel redundant runs
- Add Python 3.10, 3.11, and 3.12 matrix testing for better compatibility

.github/workflows/test.yml

@@ -6,12 +6,17 @@ on:
   pull_request:
     branches: [ main, master, develop ]
 
+# Cancel in-progress runs when a new commit is pushed
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.11']
+        python-version: ['3.10', '3.11', '3.12']
 
     steps:
     - name: Checkout code
@@ -54,7 +59,6 @@ jobs:
       run: |
         python activity_yaml_validator.py research/SPEC.yaml
         python activity_yaml_validator.py research/activity*.yaml
-      continue-on-error: true
 
   lint:
     runs-on: ubuntu-latest
@@ -79,10 +83,13 @@ jobs:
         black --check --diff .
       continue-on-error: true
 
-    - name: Lint with flake8
+    - name: Lint with flake8 (syntax errors)
       run: |
         # Stop the build if there are Python syntax errors or undefined names
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+
+    - name: Lint with flake8 (style warnings)
+      run: |
         # Exit-zero treats all errors as warnings
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
       continue-on-error: true