feat(args): add validation for training resolution

- Add validation check to ensure number of frames is multiple of 8
- Add format validation for train_resolution string (frames x height x width)

finetune/schemas/args.py

@@ -131,6 +131,24 @@ class Args(BaseModel):
             if values.get("checkpointing_steps") and v % values["checkpointing_steps"] != 0:
                 raise ValueError("validation_steps must be a multiple of checkpointing_steps")
         return v
+    
+    @field_validator("train_resolution")
+    def validate_train_resolution(cls, v: str, info: ValidationInfo) -> str:
+        try:
+            # Parse resolution string "frames x height x width"
+            frames, height, width = map(int, v.split("x"))
+            
+            # Check if frames is multiple of 8
+            if frames % 8 != 0:
+                raise ValueError("Number of frames must be a multiple of 8")
+                
+            return v
+            
+        except ValueError as e:
+            if str(e) == "not enough values to unpack (expected 3, got 0)" or \
+               str(e) == "invalid literal for int() with base 10":
+                raise ValueError("train_resolution must be in format 'frames x height x width'")
+            raise e
 
 
     @classmethod