feat: add optional ui field to CacheValue

- Add ui field to CacheValue dataclass (default None)
- Pass ui when creating CacheValue for external providers
- Use result.ui (or default {}) when returning from external cache lookup

This allows external cache implementations to store/retrieve UI data
if desired, while remaining optional for implementations that skip it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

comfy_execution/cache_provider.py

@@ -56,10 +56,11 @@ class CacheValue:
     """
     Value stored/retrieved from external cache.
 
-    Note: UI data is intentionally excluded - it contains pod-local
-    file paths that aren't portable across instances.
+    The ui field is optional - implementations may choose to skip it
+    (e.g., if it contains non-portable data like local file paths).
     """
     outputs: list  # The tensor/value outputs
+    ui: dict = None  # Optional UI data (may be skipped by implementations)
 
 
 # ============================================================

comfy_execution/caching.py

@@ -250,7 +250,7 @@ class BasicCache:
             cache_key=cache_key,
             cache_key_bytes=serialize_cache_key(cache_key)
         )
-        cache_value = CacheValue(outputs=value.outputs)
+        cache_value = CacheValue(outputs=value.outputs, ui=value.ui)
 
         for provider in get_cache_providers():
             try:
@@ -296,7 +296,7 @@ class BasicCache:
                         continue
                     # Import CacheEntry here to avoid circular import at module level
                     from execution import CacheEntry
-                    return CacheEntry(ui={}, outputs=list(result.outputs))
+                    return CacheEntry(ui=result.ui or {}, outputs=list(result.outputs))
             except Exception as e:
                 logger.warning(f"Cache provider {provider.__class__.__name__} error on lookup: {e}")