Restore GH Actions workflow.

Author: python-processing-unit

.github/workflows/run-tests.yaml

@@ -0,0 +1,53 @@
+name: Run test.pre and mypy
+
+on:
+  push:
+    branches:
+      - "**"
+  pull_request:
+    branches:
+      - "**"
+
+jobs:
+  test:
+    runs-on: windows-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Python 3.14
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.14"
+
+      - name: Install numpy, pillow, and mypy
+        run: |
+          python -m pip install --upgrade pip
+          pip install numpy pillow mypy
+        shell: pwsh
+
+      - name: Run test with prefix.exe (if present)
+        run: |
+          if (Test-Path .\prefix.exe) {
+            Write-Host "Found prefix.exe - running .\prefix.exe .\test.pre"
+            .\prefix.exe .\test.pre
+          } else {
+            Write-Host "prefix.exe not found - skipping this step"
+          }
+        shell: pwsh
+
+      - name: Run test with prefix.py (if present)
+        run: |
+          if (Test-Path .\prefix.py) {
+            Write-Host "Found prefix.py - running python .\prefix.py .\test.pre"
+            python .\prefix.py .\test.pre
+          } else {
+            Write-Host "prefix.py not found - skipping this step"
+          }
+        shell: pwsh
+
+      - name: Run mypy on selected files
+        run: |
+          Write-Host "Running mypy on: .\prefix.py .\ext\networking.py .\ext\win32.py .\lib\gui\gui.py .\lib\image\image.py"
+          python -m mypy --show-error-codes .\prefix.py .\ext\networking.py .\ext\win32.py .\lib\gui\gui.py .\lib\image\image.py
+        shell: pwsh