test_omni: add stderr capture on startup failure

modal_deploy/deploy_omni.py

@@ -925,6 +925,17 @@ def test_omni():
 
     if not ready:
         print(f"[FAIL] llama-server not ready after {time.time()-start:.0f}s")
+        # Read stderr
+        import select
+        stderr_lines = []
+        for _ in range(50):
+            line = ls_proc.stderr.readline()
+            if not line:
+                break
+            stderr_lines.append(line.rstrip())
+        print(f"[llama-server stderr] ({len(stderr_lines)} lines):")
+        for line in stderr_lines[-30:]:
+            print(f"  {line}")
         ls_proc.terminate()
         return