fix(alicode): preserve cache_control for DashScope providers (#2069)

Opt-in quirk preserveCacheControl keeps cache_control on content blocks
for alicode/alicode-intl, enabling DashScope prompt caching. signature
is always stripped; all other providers unchanged.

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/providers/registry/alicode.js

@@ -16,6 +16,7 @@ export default {
   transport: {
     baseUrl: "https://coding.dashscope.aliyuncs.com/v1/chat/completions",
     headers: {},
+    quirks: { preserveCacheControl: true },
   },
   models: [
     { id: "qwen3.5-plus", name: "Qwen3.5 Plus" },