🧩 fix: Human Message Content Handling for Legacy Content (#8525)

* wip: first pass content strings

* 📦 chore: update @langchain/core to v0.3.62 for data-provider dev dep.

* 📦 chore: bump @langchain/core to v0.3.62 for api dep.

* 📦 chore: move @langchain/core to peerDependencies in package.json and package-lock.json

* fix: update formatContentStrings to create HumanMessage directly from formatted content

* chore: import order

api/server/controllers/agents/client.js

@@ -8,6 +8,7 @@ const {
   Tokenizer,
   checkAccess,
   memoryInstructions,
+  formatContentStrings,
   createMemoryProcessor,
 } = require('@librechat/api');
 const {
@@ -16,7 +17,6 @@ const {
   GraphEvents,
   formatMessage,
   formatAgentMessages,
-  formatContentStrings,
   getTokenCountForMessage,
   createMetadataAggregator,
 } = require('@librechat/agents');