build: add codegen CI validation workflow (#725)

Author: jorgerangel-msft

.github/workflows/codegen-validation.yml

@@ -0,0 +1,67 @@
+# This workflow validates changes made to the codegen folder by running code generation
+# and ensuring the process completes successfully without errors.
+name: CodeGen Validation
+
+on:
+  pull_request:
+    paths:
+      - 'codegen/**'
+      - '.github/workflows/codegen-validation.yml'
+      - 'scripts/Invoke-CodeGen.ps1'
+    types: [opened, reopened, synchronize]
+  workflow_dispatch:
+
+jobs:
+  validate-codegen:
+    name: Validate Code Generation
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.x'
+          
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          # Use the version specified in global.json
+          global-json-file: global.json
+
+      - name: Run CodeGen Script
+        shell: pwsh
+        run: |
+          Write-Host "Running code generation validation..."
+          ./scripts/Invoke-CodeGen.ps1
+          
+          if ($LASTEXITCODE -ne 0) {
+            Write-Error "Code generation failed with exit code: $LASTEXITCODE"
+            exit $LASTEXITCODE
+          }
+          
+          Write-Host "Code generation completed successfully!"
+          
+      - name: Check for uncommitted changes
+        run: |
+          # Check if there are any changes to tracked files after code generation
+          if ! git diff --quiet; then
+            echo "::error::Code generation produced uncommitted changes. Please run the codegen script locally and commit the results."
+            echo "Changed files:"
+            git diff --name-only
+            echo "Diff details:"
+            git diff
+            exit 1
+          fi
+          
+          # Also check for untracked files that might have been generated
+          if [ -n "$(git ls-files --others --exclude-standard)" ]; then
+            echo "::error::Code generation produced untracked files. Please review and commit them if they should be included."
+            echo "Untracked files:"
+            git ls-files --others --exclude-standard
+            exit 1
+          fi
+          
+          echo "No uncommitted changes detected - code generation is up to date!"