feat: draw grid lines for selected rows cols

[BrianHung]

Explicit borders for column and row selection to match Excel. Default false so users have to opt-in.

[BrianHung]

Might update PR to show grid lines in between singleton column selections, as opposed to continuous column ranges.

[Copilot]

Pull Request Overview

This PR adds support for drawing accent-colored grid lines around selected columns and rows to match Excel-like behavior. The feature is controlled by two new optional boolean props and defaults to false, requiring users to opt-in.

• Introduces columnSelectionGridLines and rowSelectionGridLines boolean props
• Modifies the grid line drawing logic to use accent colors for boundaries between selected and unselected columns/rows
• Adds a demo story to showcase the new functionality

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
scrolling-data-grid.tsx	Passes new props through the component hierarchy
draw-grid-arg.ts	Adds the new boolean properties to the DrawGridArg interface
data-grid-render.ts	Updates drawGridHeaders calls to pass selection data when grid lines are enabled
data-grid-render.lines.ts	Implements the core logic for drawing accent-colored grid lines based on selection state
data-grid.tsx	Adds prop definitions with defaults and passes them to render function
data-grid-search.tsx	Passes new props through to underlying grid component
data-grid-dnd.tsx	Passes new props through to underlying grid component
selection-gridlines.stories.tsx	Adds Storybook demo showcasing the new feature
data-editor.tsx	Adds prop definitions and documentation for the top-level component

Comments suppressed due to low confidence (1)

[Copilot]

The documentation incorrectly states 'true (default)' but the actual default value is false as shown in line 911. The comment should say 'When true draws accent-coloured grid lines...' and '@DefaultValue false'.

Suggested change

	* @defaultValue true
	* When true draws accent-coloured grid lines around selected columns in the header. Set to false to
	* revert to the original behaviour where only the header background is accented.
	* @group Style
	* @defaultValue false

[Copilot]

The documentation incorrectly states 'true (default)' but the actual default value is false as shown in line 912. The comment should say 'When true draws accent-coloured grid lines...' and '@DefaultValue false'.

Suggested change

	* @defaultValue true
	* When true draws accent-coloured grid lines around selected rows in the header. Set to false to
	* revert to the original behaviour where only the header background is accented.
	* @group Style
	* @defaultValue false

[Copilot]

[nitpick] Trailing whitespace at the end of the file. Consider removing the space after the semicolon.

Suggested change

	};
	};