Draft-only (MTP) repos indexed as loadable models, then crash at generation: 'Qwen3_5MTPDraftModel' object has no attribute 'get_input_embeddings'

[kafasam]

Environment

• LM Studio's bundled MLX engine (observed on app-mlx-generate @34, macOS)
• Model: mlx-community/Qwen3.8-27B-MTP-4bit (draft-only / MTP repo)

Observed behavior

The draft-only MTP repo is indexed as if it were a normal runnable model:

1. It appears in the model catalog.
2. It loads successfully.
3. Every generation request then crashes deterministically with:

AttributeError: 'Qwen3_5MTPDraftModel' object has no attribute 'get_input_embeddings'

Expected behavior

Either support MTP drafting, or refuse to index/load draft-only repos with a
clear error at load time instead of a generation-time traceback.

Impact

Downstream users select these repos believing they are runnable base models;
the failure surfaces only mid-session, after load "succeeded."