chore: import upstream snapshot with attribution

servers/nextjs/utils/codexModels.ts

@@ -0,0 +1,19 @@
+export interface CodexModel {
+  id: string;
+  name: string;
+}
+
+export const CODEX_MODELS: CodexModel[] = [
+  { id: "gpt-5.5", name: "GPT-5.5" },
+  { id: "gpt-5.4", name: "GPT-5.4" },
+  { id: "gpt-5.4-mini", name: "GPT-5.4 mini" },
+  { id: "gpt-5.3-codex-spark", name: "GPT-5.3 Codex Spark (Pro preview)" },
+];
+
+export const DEFAULT_CODEX_MODEL = "gpt-5.5";
+
+const CODEX_MODEL_IDS = new Set(CODEX_MODELS.map((model) => model.id));
+
+export function isSupportedCodexModel(model?: string): boolean {
+  return Boolean(model && CODEX_MODEL_IDS.has(model));
+}