refactor(select): use Base UI native placeholder prop

[invisal]

Summary

Since we have upgraded to BaseUI to 1.2.0, we can now use the native placeholder (https://base-ui.com/react/overview/releases/v1-1-0#select). This simplifies the Select component's implementation by removing the need to manually inject placeholder items into the items array.

Benefits

• Cleaner API: More intuitive placeholder API that aligns with standard HTML select behavior
• Reduced complexity: Removes placeholder item injection logic from the Select component
• Backward compatible: Maintains support for the null-value placeholder pattern
• Better filtering: Automatically filters null-value items from auto-rendered options

Changes

• Added placeholder prop support to Select.Value component
• Removed manual placeholder item injection logic
• Added comprehensive test coverage for placeholder functionality
• Updated documentation to show both placeholder approaches
• Added changeset for patch release

Testing

• ✅ Comprehensive test suite covering all placeholder scenarios
• ✅ Both placeholder prop and null-value item patterns tested
• ✅ Controlled component behavior verified

[pkg-pr-new]

npm i https://pkg.pr.new/@cloudflare/kumo@172

commit: 59467a9

[github-actions]

Docs Preview

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Commit: e39738d

[mattrothenberg]

Awesome! This is a great improvement.

[github-actions]

Visual Regression Report

13 screenshot(s) with visual changes:

Button / Loading State

0 px (0%) changed

Before	After	Diff

Dialog / Alert Dialog (role="alertdialog")

33,241 px (0.63%) changed

Before	After	Diff

Dialog / With Combobox

153,623 px (2.93%) changed

Before	After	Diff

Dialog / With Dropdown

154,846 px (2.95%) changed

Before	After	Diff

Select / Basic Usage

379,150 px (40.38%) changed

Before	After	Diff

Select / Basic Label and Value

16,154 px (1.62%) changed

Before	After	Diff

Select / Placeholder

380,935 px (36.74%) changed

Before	After	Diff

Select / Custom Rendering

0 px (0%) changed

Before	After	Diff

Select / Loading

258 px (0.04%) changed

Before	After	Diff

Select / Multiple Item

0 px (0%) changed

Before	After	Diff

Select / More Example

0 px (0%) changed

Before	After	Diff

Select / Select.Option

24,948 px (2.91%) changed

Before	After	Diff

Select (Open)

1,338,837 px (10.63%) changed

Before	After	Diff

11 screenshot(s) unchanged

• Button / Variants
• Button / Sizes
• Button / With Icon
• Button / Icon Only
• Button / Disabled State
• Dialog / Basic Dialog
• Dialog / Confirmation Dialog (with disablePointerDismissal)
• Dialog / With Actions
• Dialog / With Select
• Dialog (Open)
• Select / Select

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Generated by Kumo Visual Regression