Fix Windows CI: pin to windows-2022, bump actions/checkout to v6.0.3 (#81)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
       matrix:
         os: [macos-latest, ubuntu-latest]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6.0.3
       with:
         persist-credentials: false
     - run: npm ci
@@ -23,9 +23,9 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [windows-latest]
+        os: [windows-2022]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6.0.3
       with:
         persist-credentials: false
     - run: npm ci