Add CI workflow for standard/explicit tests; update docs

Introduced a GitHub Actions workflow (ci.yml) with separate jobs for standard and explicit-mode tests, including artifact handling and conditional blocking for branch protection. Updated README to document CI requirements for main/dev branches and clarify fork PR settings.

Author: kzdev-net

.github/workflows/ci.yml

@@ -0,0 +1,80 @@
+name: CI
+
+on:
+  push:
+    branches: [main, dev]
+  pull_request:
+    branches: [main, dev]
+
+jobs:
+  test-standard:
+    name: test-standard
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 10.x
+
+      - name: Restore
+        run: dotnet restore Source/KZDev.PerfUtils.sln
+
+      - name: Build
+        run: dotnet build Source/KZDev.PerfUtils.sln -c Release
+
+      - name: Test (standard)
+        run: dotnet test Source/KZDev.PerfUtils.sln -c Release --no-build
+
+      - name: Upload Release artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: test-release-artifacts
+          path: artifacts
+          if-no-files-found: error
+
+  test-explicit:
+    name: test-explicit
+    needs: [test-standard]
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    # test-explicit failures are non-blocking only for PRs whose base is not main, or for pushes to dev.
+    # They remain blocking for PRs into main and for pushes to main (aligned with branch-protection intent).
+    continue-on-error: ${{ (github.event_name == 'pull_request' && github.base_ref != 'main') || (github.event_name == 'push' && github.ref == 'refs/heads/dev') }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 10.x
+
+      - name: Download build artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: test-release-artifacts
+          path: artifacts
+
+      - name: Apply serialized xUnit runner for Explicit
+        run: |
+          set -euo pipefail
+          count=0
+          while IFS= read -r -d '' f; do
+            cp Source/Tst/xunit.runner.explicit.json "$f"
+            count=$((count + 1))
+          done < <(find artifacts/bin -name xunit.runner.json -print0)
+          if [ "$count" -eq 0 ]; then
+            echo "No xunit.runner.json found under artifacts/bin; cannot apply explicit runner overlay."
+            exit 1
+          fi
+          echo "Overlay applied to ${count} xunit.runner.json file(s)."
+
+      - name: Test (Explicit only, sequential xUnit)
+        run: |
+          dotnet test Source/KZDev.PerfUtils.sln -c Release --no-build \
+            --filter "TestMode=Explicit" \
+            -- xUnit.Explicit=only xUnit.MaxParallelThreads=1 xUnit.ParallelizeAssembly=false xUnit.ParallelizeTestCollections=false

Source/Tst/README.md

@@ -63,6 +63,17 @@ Add **`[Trait(TestConstants.TestTrait.TestMode, TestConstants.TestMode.Explicit)
 
 ---
 
+## Maintainers: branch protection (CI)
+
+Configure GitHub **branch protection** status checks to match how CI gates merges:
+
+- **`main`:** Require **`test-standard`** and **`test-explicit`** from the **CI** workflow so both jobs must pass before merge.
+- **`dev`:** Require **`test-standard`** only. **`test-explicit`** is informational on `dev` (workflow uses `continue-on-error` for pushes to `dev` and for pull requests whose base branch is not `main`).
+
+Fork pull requests need repository settings that allow GitHub Actions to run from forks if you want CI for external contributors.
+
+---
+
 ## Linux: Docker-based test run
 
 > Run these commands from the \{RepositoryRoot\}\Source directory