Fix text cache source_path_in_name: prompt_path -> image_path

'prompt_path' doesn't exist as a pipeline name, so _get_source_path
returned None for every text cache lookup, causing 100% cache misses
and device mismatch errors when the text encoder was on CPU during
training. Use 'image_path' as the key, matching the old DiskCache
behavior.

Author: BitcrushedHeart

modules/dataLoader/mixin/DataLoaderText2ImageMixin.py

@@ -400,7 +400,7 @@ def before_cache_text_fun():
 
         text_disk_cache = SmartDiskCache(cache_dir=text_cache_dir, split_names=text_split_names, aggregate_names=[], variations_in_name='concept.text_variations', balancing_in_name='concept.balancing', balancing_strategy_in_name='concept.balancing_strategy',
                                         variations_group_in_name=['concept.path', 'concept.seed', 'concept.include_subdirectories', 'concept.text'], group_enabled_in_name='concept.enabled', before_cache_fun=before_cache_text_fun,
-                                        modeltype=config.model_type.value, source_path_in_name='prompt_path', sourceless=sourceless)
+                                        modeltype=config.model_type.value, source_path_in_name='image_path', sourceless=sourceless)
 
         modules = []