Support Inline-Edit in IntelliJ Plugin

[icycodes]

The inline-edit feature is already supported in the VSCode extension. Users can select some text (optionally), invoke inline-edit (using Ctrl+I or selecting it from the context menu), input an instruction to edit the current file, then review the changes and accept or discard them.
We want to support this feature in the IntelliJ plugin as well.

The IntelliJ platform provides a code-intentions-preview api that can be used for reviewing changes and resolving edits. This should be a better approach than manually using color decoration for diffs, which is implemented in the VSCode extension.

The underlying inline-edit implementation is in tabby-agent, which exports an extended LSP method ChatEditRequest. It currently supports output in previewChanges format only (used in VSCode extension). We may need to modify it to support a direct editing format to make the result compatible with the IntelliJ code-intentions-preview API.

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Please reply with a 👍 if you want this feature.

[zhanba]

I would like to take this issue.

On how to display code diff:

• Code intention preview is displayed when you hover on code intention, and disappeared when you move off. So it's hard to use it in inline chat which need first trigger a chat input and then display diff.
  

• To display inline code diff, we can display a code diff editor on inline chat area ( a customized component inserted between code lines) or we can just add color decoration like VSCode extension did. I'd like to know which one you prefer?

[icycodes]

I would like to take this issue.

On how to display code diff:

• Code intention preview is displayed when you hover on code intention, and disappeared when you move off. So it's hard to use it in inline chat which need first trigger a chat input and then display diff.
  
• To display inline code diff, we can display a code diff editor on inline chat area ( a customized component inserted between code lines) or we can just add color decoration like VSCode extension did. I'd like to know which one you prefer?

Thank you for pointing this out. It seems there isn't an API available to manually control the display and hiding of the code-intention-preview component. I will update the issue description accordingly.

I agree that implementing it similar to how is done in the VSCode extension would be a good approach for now.