fix(skill): patch up skill diffing code (#758)

Co-authored-by: Letta <noreply@letta.com>

src/agent/memory.ts

@@ -4,6 +4,7 @@
  */
 
 import type { CreateBlock } from "@letta-ai/letta-client/resources/blocks/blocks";
+import { READ_ONLY_BLOCK_LABELS } from "./memoryConstants";
 import { MEMORY_PROMPTS } from "./promptAssets";
 
 /**
@@ -33,11 +34,7 @@ export type MemoryBlockLabel = (typeof MEMORY_BLOCK_LABELS)[number];
  * Block labels that should be read-only (agent cannot modify via memory tools).
  * These blocks are managed by specific tools (e.g., Skill tool for skills/loaded_skills).
  */
-export const READ_ONLY_BLOCK_LABELS = [
-  "skills",
-  "loaded_skills",
-  "memory_filesystem",
-] as const;
+export { READ_ONLY_BLOCK_LABELS };
 
 /**
  * Block labels that should be isolated per-conversation.