Install PowerShell in Gitea build runner

.gitea/workflows/client-build.yml

@@ -45,6 +45,39 @@ jobs:
         with:
           dotnet-version: "10.0.x"
 
+      - name: Install PowerShell
+        shell: bash
+        run: |
+          set -euo pipefail
+          if command -v pwsh >/dev/null 2>&1; then
+            pwsh --version
+            exit 0
+          fi
+
+          if [ "$(id -u)" -eq 0 ]; then
+            SUDO=""
+          elif command -v sudo >/dev/null 2>&1; then
+            SUDO="sudo"
+          else
+            echo "PowerShell is missing and this runner cannot install packages."
+            exit 1
+          fi
+
+          . /etc/os-release
+          case "$ID" in
+            ubuntu) MICROSOFT_REPO="https://packages.microsoft.com/config/ubuntu/${VERSION_ID}/packages-microsoft-prod.deb" ;;
+            debian) MICROSOFT_REPO="https://packages.microsoft.com/config/debian/${VERSION_ID}/packages-microsoft-prod.deb" ;;
+            *) echo "Unsupported runner distribution: $ID"; exit 1 ;;
+          esac
+
+          $SUDO apt-get update
+          $SUDO apt-get install -y ca-certificates curl
+          curl -fsSL "$MICROSOFT_REPO" -o /tmp/packages-microsoft-prod.deb
+          $SUDO dpkg -i /tmp/packages-microsoft-prod.deb
+          $SUDO apt-get update
+          $SUDO apt-get install -y powershell
+          pwsh --version
+
       - name: Build client package
         shell: pwsh
         run: |