feat: add TreeView Component

[JoshMK]

Closes:

https://github.com/dequelabs/axe-reports/issues/2952
#1290

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[Copilot]

Pull request overview

This PR introduces a new TreeView component to the Cauldron design system, enabling users to display and interact with hierarchical tree structures with support for single/multiple selection modes and custom actions.

Changes:

• Added TreeView component with TreeViewItem subcomponent supporting single/multiple selection modes
• Integrated react-aria-components library for accessibility features
• Added CSS styling for tree view with theme support
• Created comprehensive test coverage for TreeView functionality

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/styles/tree-view.css	CSS styles for TreeView component with light/dark theme support
packages/styles/index.css	Import statement for tree-view.css
packages/react/src/index.ts	Export statement for TreeView component
packages/react/src/components/TreeView/index.tsx	Main TreeView component definition
packages/react/src/components/TreeView/TreeViewItem.tsx	TreeViewItem subcomponent with selection handling
packages/react/src/components/TreeView/TreeView.test.tsx	Test suite for TreeView component
packages/react/src/components/Checkbox/index.tsx	Added onChangeToggle prop to Checkbox component
packages/react/package.json	Added react-aria-components dependency
package.json	Added packageManager field
docs/pages/components/TreeView.mdx	Documentation for TreeView component

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[dbjorge]

It'd be good to go back to design and clarify the expected behavior of the checkboxes - the figma doesn't clarify explicitly, but some of the examples it cites (eg, Fluent 2) use a pattern where selecting a parent would implicitly select all children, and unselecting a child would implicitly set the parent to either an indeterminate or unselected state (depending on if other siblings were still selected).

adobe/react-spectrum#6589 suggests that it might be challenging to actually implement that ourselves without patching the spectrum tree view and that we'd likely prefer to wait for adobe/react-spectrum#8800 rather than implement it ourselves, but we should make sure that stakeholders/design are ok with the current behavior in the meantime.

[JoshMK]

It'd be good to go back to design and clarify the expected behavior of the checkboxes - the figma doesn't clarify explicitly, but some of the examples it cites (eg, Fluent 2) use a pattern where selecting a parent would implicitly select all children, and unselecting a child would implicitly set the parent to either an indeterminate or unselected state (depending on if other siblings were still selected).

adobe/react-spectrum#6589 suggests that it might be challenging to actually implement that ourselves without patching the spectrum tree view and that we'd likely prefer to wait for adobe/react-spectrum#8800 rather than implement it ourselves, but we should make sure that stakeholders/design are ok with the current behavior in the meantime.

Good points, Dan. Also a quick technical note for anyone reviewing this:

Adobe actually has two component libraries available that we can use - Spectrum and React Aria Components. I ended up choosing React Aria Components since unlike Spectrum, it doesn't make style assumptions and allows us to incorporate our existing Deque theming into new components.