Revert "LLMs: OpenAI Responses API by default for new models. Fixes #937"

This caused all unknown models to default to the responses API.
We need heuristics for determining OpenAI vs OpenAI-compatible.

This reverts commit a6862d8c58.

src/modules/llms/server/openai/models/openai.models.ts

@@ -945,7 +945,7 @@ export const _fallbackOpenAIModel: KnownModel = {
   description: 'Unknown, please let us know the ID. Assuming a context window of 128k tokens, and a maximum output of 4k tokens.',
   contextWindow: 128000,
   maxCompletionTokens: 4096,
-  interfaces: [...IFS_CHAT_MIN, LLM_IF_OAI_Responses], // Use Responses API by default for new models
+  interfaces: IFS_CHAT_MIN,
   // hidden: true,
 };