fix: add signing key diagnostic

.github/workflows/release.yml

@@ -33,6 +33,19 @@ jobs:
 
       - run: pnpm install --frozen-lockfile
 
+      # 诊断：确认签名密钥已注入
+      - name: Verify signing key
+        shell: pwsh
+        env:
+          TAURI_SIGNING_PRIVATE_KEY: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY }}
+        run: |
+          if ([string]::IsNullOrEmpty($env:TAURI_SIGNING_PRIVATE_KEY)) {
+            Write-Error "TAURI_SIGNING_PRIVATE_KEY is EMPTY - update bundles will not be generated!"
+            exit 1
+          }
+          $lines = $env:TAURI_SIGNING_PRIVATE_KEY.Split("`n").Count
+          Write-Host "TAURI_SIGNING_PRIVATE_KEY is set ($lines lines)"
+
       # 构建 Tauri 应用，tauri-action 自动签名并创建 GitHub Release
       - name: Build & Release
         uses: tauri-apps/tauri-action@v0