fix: 🔧 default llm config being used for graph store instead of root llm config provided by the user

[ranjithkumar8352]

Description

If the user has provided a config with llm in the main config then that should be used for graph store but instead the default open ai config is used.

The user-provided llm config works for graph store only if it is provided in the graphStore config.

Fixes #3425

This also includes a small change in anthropic.ts because the build fails without this change.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested locally using npm link

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed

[whysosaket]

Hey @ranjithkumar8352, have you tried and tested if this works? As far as I know, the reason we defaulted the config for Graph Store was because of the use of structured schema and the zod schema there.