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>

tests/__baseline__/alias-baseline.json

@@ -105,7 +105,7 @@
     "claude": "cc",
     "cline": "cl",
     "cloudflare-ai": "cloudflare-ai",
-    "codebuddy-cn": "codebuddy-cn",
+    "codebuddy-cn": "cbcn",
     "codex": "cx",
     "cohere": "cohere",
     "commandcode": "commandcode",
@@ -164,6 +164,7 @@
     "black-forest-labs",
     "blackbox",
     "byteplus",
+    "cbcn",
     "cc",
     "cerebras",
     "cl",
@@ -231,4 +232,4 @@
     "xiaomi-mimo",
     "xiaomi-tokenplan"
   ]
-}
+}