Theia LLM - Polish of contribution

[sdirix]

Overview

This is a ticket to manage the direct follow up of the initial Theia AI support contribution (#14048)

Tasks

Architecture

These tasks / evaluations challenge major parts of the contributed Theia AI architecture

• Streamline AI Variable Service #14817 @CamilleLetavernier
• The AI configuration view partially competes with the preferences. It must be evaluated whether they can be (partially) merged and how the new role of the configuration view then looks like.

Major impact

• Remove AIEditorManager #14873
• Rework and improve Agent and ChatModel API #14818 @eneufeld
• It must be discussed whether we want to adapt the ai code completion items or remove them. We will definitively keep the inline suggestions.
  • they were removed -> chore: polish AI code completion #14192
• User edited prompt templates are stored in separate configurable directories. For this a already layered mechanism can be used.

Best practices

• Improve chat model naming #14872
• Make the model fields readonly where applicable.
• Remove redundant types in response parts by using readonly -> remove type duplication for kind property #14207
• Rename and refactor the language model delegation mechanic. Some of the used classes/services can be merged and they should follow the Theia conventions for naming.
• All Theia AI strings should be translatable #14825 @CamilleLetavernier
• A user message was shown by customizing the MonacoEditorProvider in the same way as the EditorManager. This was removed from the contribution. However it would be great to get the customization back in. This must be evaluated.
• The contribution introduces a new offset interface. It should be checked whether it can be replaced with an already existing concept in Theia.

Other medium to minor improvements

• Prompts implementation can be improved
• Use a registry for response merging to allow for advanced use cases
• Some of the new variables are contributed one at a time in separate contributions. They should be merged.
• Improve on agent interface namings
• Rework the language model implementation (methods, jsdoc, etc.)
• Remove the distinction between asString() returning undefined and being undefined
• Make sessions disposable
• Inline constants which are used only once
• Improve AI history implementation
• Improve AI terminal implementation
• Improve the core protocol