ci: add Gitea Actions smoke workflow for the self-hosted Windows runner

.gitea/workflows/smoke.yml

@@ -0,0 +1,21 @@
+# Gitea Actions smoke test for the self-hosted Windows runner (RARE-win).
+# Deliberately uses NO `uses:` steps: Gitea resolves actions from
+# data.forgejo.org, which does not carry actions/checkout@v6 or
+# actions/setup-dotnet@v4, so the .github workflows cannot run here as-is.
+# This proves runner execution independently of that.
+name: smoke
+on:
+  workflow_dispatch:
+
+jobs:
+  windows-smoke:
+    runs-on: windows-latest
+    steps:
+      - name: Report the build environment
+        shell: pwsh
+        run: |
+          Write-Host "host   : $env:COMPUTERNAME"
+          Write-Host "user   : $env:USERNAME"
+          Write-Host "cores  : $env:NUMBER_OF_PROCESSORS"
+          dotnet --list-sdks
+          git --version