refactor: expose CacheProvider API via comfy_api.latest.Caching

- Add Caching class to comfy_api/latest/__init__.py that re-exports
  from comfy_execution.cache_provider (source of truth)
- Fix docstring: "Skip large values" instead of "Skip small values"
  (small compute-heavy values are good cache targets)
- Maintain backward compatibility: comfy_execution.cache_provider
  imports still work

Usage:
    from comfy_api.latest import Caching

    class MyProvider(Caching.CacheProvider):
        def on_lookup(self, context): ...
        def on_store(self, context, value): ...

    Caching.register_provider(MyProvider())

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

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

comfy_execution/cache_provider.py

@@ -4,6 +4,9 @@ External Cache Provider API for distributed caching.
 This module provides a public API for external cache providers, enabling
 distributed caching across multiple ComfyUI instances (e.g., Kubernetes pods).
 
+Public API is also available via:
+    from comfy_api.latest import Caching
+
 Example usage:
     from comfy_execution.cache_provider import (
         CacheProvider, CacheContext, CacheValue, register_cache_provider
@@ -120,7 +123,7 @@ class CacheProvider(ABC):
 
         Common filters:
             - By class_type: Only expensive nodes (KSampler, VAEDecode)
-            - By size: Skip small values (< 1MB)
+            - By size: Skip large values to reduce network overhead
 
         Default: Returns True (cache everything).
         """