feat: support modelTypes whitelist for discovered LM Studio models

[scott1028]

Summary

This PR adds support for filtering auto-discovered LM Studio models via provider.lmstudio.options.modelTypes.

Previously, the plugin always added every discovered model that was not already configured. With this change, users can optionally whitelist discovered models by type.

Supported values:

• chat
• embedding
• unknown

The legacy options.model_types key is also preserved for backward compatibility.

Changes

• add modelTypes / model_types parsing in config enhancement
• filter discovered models before adding them to provider.lmstudio.models
• validate configured model type values
• add a validation hint for the common typo embedded -> embedding
• document the new modelTypes option in the README
• add test coverage for:
  • baseline behavior when modelTypes is not configured
  • filtering by chat
  • filtering by unknown
  • invalid modelTypes values
  • typo suggestion for embedded
  • backward compatibility for legacy model_types

Behavior Notes

• modelTypes is currently inferred from the LM Studio model id, not from a dedicated type field returned by the API.
• unknown means the discovered model ID does not match the plugin's current chat or embedding categorization rules.

Testing

• npm run test:run
• all tests passed (22/22)