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

• The initial contribution adds an own AI variable service. Theia already has a generic variable service. It must be evaluated whether they should be fully merged instead of just integrated as they are right now.
• 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

• The original contribution customizes the EditorManager in the AIEditorManager and rebinds it. This is problematic for downstream projects which also rebind the EditorManager. The editor manager enhancements should be merged into the base implementation instead.
• The agent inheritance tree is quite large already. It must be checked whether it can be simplified, including using composition patterns over inheritance.
• 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

• Rename ChatModel/ChatModelImpl, ResponseModel/ResponseModelImpl pairs to be ChatMode/MutableChatModel, ResponseModel/MutableResponseModel instead to better indicate their roles in the system.
• 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.
• Introduce i18n for all hard coded strings
• 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