fix(studio): probe returns knownModels when /models is unavailable

When discoveredModels is empty and probe succeeds, return the full
knownModels list (7 for MiniMax) instead of just the probed model.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/studio/src/api/server.ts

@@ -482,7 +482,7 @@ async function probeServiceCapabilities(args: {
         await chatCompletion(client, model, [{ role: "user", content: "ping" }], { maxTokens: 2048 });
         const models = discoveredModels.length > 0
           ? discoveredModels
-          : [{ id: model, name: model }];
+          : preset?.knownModels?.map((id) => ({ id, name: id })) ?? [{ id: model, name: model }];
         return {
           ok: true,
           models,