feat(providers): add Alibaba Token Plan (token-plan.ap-southeast-1)

Fourth Alibaba key type — Coding Plan (alicode/alicode-intl) and Model Studio
(alims-intl) both reject Token Plan keys. Registry entry only; PROVIDER_MODELS
builds from providers/registry so no executor or translator work is needed.

Singapore-only (eu-central-1 answers IllegalEndpoint) and OpenAI-compatible
transport only (the Anthropic surface is not authorized for this plan).

Closes #2754
Closes #2806

open-sse/providers/registry/index.js

@@ -120,6 +120,7 @@ import p117 from "./selfhosted-stt.js";
 import p118 from "./selfhosted-tts.js";
 import p119 from "./selfhosted-embedding.js";
 import p120 from "./fish-audio.js";
+import p121 from "./alitp-intl.js";
 
 export default [
   p0,
@@ -241,4 +242,5 @@ export default [
   p118,
   p119,
   p120,
+  p121,
 ];