feat: add GitHub OIDC token fetching for Azure signing in desktop release workflow

- Implemented a step to fetch the GitHub OIDC token for Azure signing SDK when signing is enabled.
- Updated environment variables for Azure.Identity EnvironmentCredential to support the TrustedSigning PowerShell module.

.github/workflows/desktop-release.yml

@@ -83,6 +83,16 @@ jobs:
           tenant-id: ${{ secrets.AZURE_TENANT_ID }}
           subscription-id: ${{ secrets.AZURE_SUBSCRIPTION_ID }}
 
+      - name: Fetch GitHub OIDC token for Azure signing SDK
+        if: steps.sign.outputs.enabled == 'true'
+        id: oidc
+        shell: pwsh
+        run: |
+          $token = (Invoke-RestMethod -Headers @{Authorization = "bearer $env:ACTIONS_ID_TOKEN_REQUEST_TOKEN"} `
+            -Uri "$env:ACTIONS_ID_TOKEN_REQUEST_URL&audience=api://AzureADTokenExchange").value
+          Write-Output "::add-mask::$token"
+          "token=$token" | Out-File -FilePath $env:GITHUB_OUTPUT -Encoding utf8 -Append
+
       - name: Setup pnpm
         uses: pnpm/action-setup@v5
 
@@ -144,3 +154,8 @@ jobs:
           AZURE_CODESIGN_ENDPOINT: ${{ vars.AZURE_CODESIGN_ENDPOINT }}
           AZURE_CODESIGN_ACCOUNT: ${{ vars.AZURE_CODESIGN_ACCOUNT }}
           AZURE_CODESIGN_PROFILE: ${{ vars.AZURE_CODESIGN_PROFILE }}
+          # Env vars for Azure.Identity EnvironmentCredential used by the TrustedSigning PowerShell module.
+          # Only populated when signing is enabled; harmless when empty otherwise.
+          AZURE_TENANT_ID: ${{ steps.sign.outputs.enabled == 'true' && secrets.AZURE_TENANT_ID || '' }}
+          AZURE_CLIENT_ID: ${{ steps.sign.outputs.enabled == 'true' && secrets.AZURE_CLIENT_ID || '' }}
+          AZURE_FEDERATED_TOKEN: ${{ steps.oidc.outputs.token }}