Slider and consistent component APIs

A new Slider component, consistent field roots, and fixes for selection menus and modal backdrops.

New features

• Added Slider with single-value and range modes, horizontal and vertical orientations, controlled and uncontrolled state, keyboard input, value tooltips, and separate change and commit callbacks. It composes with labels, helper text, and error messages.

Improvements

• Changed the BreakpointsIndicator default corner to bottom-end and raised its default z-index.

Bug fixes

• Fixed multi-select rows showing a persistent background when selected. Selection now shows through the checkbox only.
• Fixed clicking an empty Select.Combobox search field not closing the open menu.
• Fixed blurred Modal backdrops not dimming as much as the dim variant.

Breaking changes

• Replaced the standalone Select, TextField, and TextArea roots with Select.Root, TextField.Root, and TextArea.Root. Existing .Root usage is unchanged.

// Before
<Select {...props} />
<TextField {...props} />

// After
<Select.Root {...props} />
<TextField.Root {...props} />

• Replaced shape="rounded" with rounded and shape="square" with rounded={false} on Dismissible, Modal.Dismissible, and BreakpointsIndicator.
• Changed Dismissible to a square close button by default. Pass rounded to keep the previous appearance.