feat(codebuddy-cn): add short model prefix alias "cbcn"

codebuddy-cn shipped without a short alias, making its model prefix the
longest of any provider (codebuddy-cn/glm-5.2). Add alias + uiAlias
"cbcn" so the prefix becomes cbcn/glm-5.2, consistent with qoder (qd),
kiro (kr), codex (cx). "cbcn" = CodeBuddy CN; reserves "cbai" for a
future codebuddy-ai (intl) provider.

Backward-compatible: full id codebuddy-cn/... still resolves (resolver
matches both id and alias).

Also regenerate tests/__baseline__/alias-baseline.json: idToAlias entry
codebuddy-cn now maps to cbcn, and cbcn joins the sorted modelKeys list.

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

open-sse/providers/registry/codebuddy-cn.js

@@ -1,5 +1,9 @@
 export default {
   id: "codebuddy-cn",
+  // Short model prefix (cbcn/glm-5.2). "cbcn" = CodeBuddy CN; reserve "cbai"
+  // for a future codebuddy-ai (intl) provider. The full id still resolves.
+  alias: "cbcn",
+  uiAlias: "cbcn",
   hidden: false,
   priority: 90,
   display: {