Release inactive backend before GPU model switching

README.md

@@ -178,6 +178,9 @@ When DA3 is selected, its depth, confidence, extrinsics, and intrinsics shapes
 are validated at the adapter boundary; malformed results trigger the labeled V2
 fallback before any geometry export begins, and the exact fallback exception is
 stored in the run manifest for diagnosis.
+Backend switching also releases the previously loaded heavyweight model before
+loading the next one, reducing avoidable GPU memory pressure in long-lived
+Space processes.
 The baseline requirements also pin the CUDA-compatible Torch pair and bound
 dependency major versions so rebuilds do not silently change the inference or
 export contract.