ci: 修复 workflow YAML + 打包脚本；忽略 runtime/（含 runner 凭据，勿提交）

- heredoc 改为 scripts/build-online.py 调用（YAML merge key 语法修复）
- .gitignore 忽略 runtime/（act-runner 凭据 .runner 及二进制）

scripts/build-online.py

@@ -0,0 +1,12 @@
+"""Build dsh-desktop-online.zip from the current working directory."""
+import zipfile, os, sys
+
+out = sys.argv[1] if len(sys.argv) > 1 else '../dsh-desktop-online.zip'
+count = 0
+with zipfile.ZipFile(out, 'w', zipfile.ZIP_DEFLATED) as z:
+    for r, _, fs in os.walk('.'):
+        for f in fs:
+            p = os.path.join(r, f)
+            z.write(p, os.path.relpath(p, '.'))
+            count += 1
+print('ZIP:', out, '%.1f MB' % (os.path.getsize(out) / 1048576), count, 'files')