refactor: rename provider to alicode (Aliyun Coding)

Rename alicloud to alicode to clearly indicate Aliyun's Coding Plan service.

- Provider ID: alicode (short for Aliyun Coding)
- Model format: alicode/qwen3.5-plus
- Simplified mapping - no more bidirectional aliases

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

open-sse/config/constants.js

@@ -175,7 +175,7 @@ export const PROVIDERS = {
     },
     clientVersion: "1.1.3"
   },
-  alicloud: {
+  alicode: {
     baseUrl: "https://coding.dashscope.aliyuncs.com/v1/chat/completions",
     format: "openai",
     headers: {}