Summary

Closes #5316

• Bump dependencies: Updated @librechat/agents, @langchain/core, and related packages
• Implement prompt caching for Anthropic Agents: Added cache control logic in Anthropic prompt handling by refining message type checks to support caching.
• Extract helper functions: Refactored AnthropicClient by moving header configuration and reasoning settings into dedicated helper functions.
• Update LLM configuration: Integrated helper functions into Anthropic LLM settings for dynamic header generation based on the model.

Other Changes

• Deprecate outdated models: Replaced the deprecated Gemini-2.0 flash lite preview identifier with the current supported version.
• Enhance accessibility: Fixed AgentPanel and AgentSelect focus issues by enforcing consistent component tree rendering and maintaining ComboBox focus during agent ID changes.
• Migrate form logic: Moved react-hook-form Controller logic from AgentPanel to AgentSelect and removed auto-focus to streamline form interactions.