Add setting to preserve current line highlight during text selection

[Copilot]

Fixes #issue_number

Description

Current line highlight disappears when text is selected. This adds editor.cursorSurroundingLinesHighlightOnSelection (default: false) to control this behavior.

Changes:

• Added boolean option to IEditorOptions with default false for backward compatibility
• Modified AbstractLineHighlightOverlay._shouldRenderInContent() to render when selection exists if option enabled
• Updated enum values in EditorOption, monaco.d.ts, and standaloneEnums.ts
• Added test coverage for option toggle behavior

Implementation:

protected _shouldRenderInContent(): boolean {
    return (
        (this._renderLineHighlight === 'line' || this._renderLineHighlight === 'all')
        && (this._selectionIsEmpty || this._cursorSurroundingLinesHighlightOnSelection)
        && (!this._renderLineHighlightOnlyWhenFocus || this._focused)
    );
}

Users can enable via Settings UI or:

{
  "editor.cursorSurroundingLinesHighlightOnSelection": true
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>BUG: No highlight of current line if selected any word in this line</issue_title>
<issue_description>

Does this issue occur when all extensions are disabled?: Yes

Version: 1.101.1 (user setup)
Commit: 18e3a1e

Type: Bug

STR with screenshots:

1. We can see current line highlight

2. Select word test and highlight of current line disappears (only words are highlighted):

Comments on the Issue (you are @copilot in this section)

@alexdima The current implementation hides the current line highlight when there is a selection (this behavior is consistent to other editors). PR welcome if you would like to add a setting to tweak that. @alexdima Sure, here is for example Sublime Text:

https://github.com/user-attachments/assets/c99c3a8b-f715-44cd-996c-2f9880d149bb</comment_new>
<comment_new>@alexdima
@psnet Would you like to contribute a PR? I am open to having an option to control this.</comment_new>
<comment_new>@alexdima
Let's see if Copilot can do it :) </comment_new>

• Fixes BUG: No highlight of current line if selected any word in this line #229539

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