manager: classify gguf by resolving alias to a local .gguf file

load_model() decided gguf-vs-HF purely from the literal string 'gguf' in
the model name. A gguf whose alias carries only the quant suffix (e.g.
'coe-gemma4-coding-hc-14b-a4b-q4_k_m', no literal 'gguf') was mis-routed
to the HF/transformers backend, which then failed with "is not a valid
model identifier" (503). Fall back to _resolve_local_gguf(): if the alias
maps to an actual local .gguf, treat it as gguf and route to llama.cpp.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

codai/models/manager.py

@@ -323,9 +323,18 @@ class ModelManager:
 
         available = detect_available_backends()
 
-        # Check if model is a GGUF file
+        # Check if model is a GGUF file. The name alone isn't reliable: a gguf's
+        # alias may carry only the quant suffix (e.g. '…-q4_k_m') with no literal
+        # 'gguf', which would mis-route it to the HF/transformers path. Fall back
+        # to resolving the alias to an actual local .gguf file.
         is_gguf = model_name.endswith('.gguf') or 'gguf' in model_name.lower()
-        
+        if not is_gguf:
+            try:
+                if _resolve_local_gguf(model_name):
+                    is_gguf = True
+            except Exception:
+                pass
+
         # Determine backend
         if backend_type == "auto":
             if available.get('nvidia'):