Add SlidingButton component

[Deliaz]

Summary

Adds the SlidingButton (swipe-to-confirm) component to the Base Design System. Uses a drag gesture instead of a tap to confirm actions, reducing accidental triggers and reinforcing user intent by introducing deliberate friction.

Props

Prop	Type	Default	Description
label	string	(required)	Text displayed on the track and repeated on the slider once completed
threshold	'high' | 'low'	'high'	Drag distance required — high = 80%, low = 20% of track width
isLoading	boolean	false	Shows a loading spinner, hides label and grabber, blocks interaction
isDisabled	boolean	false	Grays out the component, blocks all interaction
onComplete	() => void	—	Callback fired once when the drag threshold is met or Enter/Space is pressed
slideBackAfterMs	number	—	Auto-resets the button to idle state after N ms
overrides	SlidingButtonOverrides	{}	Override any of the 8 sub-elements: Root, Track, Slider, Label, CompletedLabel, Grabber, LoadingOverlay, LoadingSpinner
aria-label	string	—	Custom accessible label; defaults to label if not provided

Docs

Light theme	Dark Theme

Ladle stories

What's included

• Component (src/sliding-button/): constants, types, default-props, styled-components, component, index
• Documentation: MDX page with Yard interactive playground, 3 example files (basic, states, low-threshold)

Test plan

• TypeScript passes with zero errors from new files
• Prettier formatting clean
• npm run build:lib compiles successfully

[hualf1995]

1. Can you try to run the documentation site app locally and attach a screenshot in the PR description? I feel you may need to add it to route to make it show up in doc site. You can use this script to develop on doc site: https://github.com/uber/baseweb/blob/main/package.json#L16
2. Can you add __tests__ for this component? (Unit tests and ubook stories can be added to this folder) You can start ubook dev with this script: https://github.com/uber/baseweb/blob/main/package.json#L17
3. Can you please bump the package version? Since it is a new component, I believe npm version minor is fine.

[Deliaz]

1. Can you try to run the documentation site app locally and attach a screenshot in the PR description? I feel you may need to add it to route to make it show up in doc site. You can use this script to develop on doc site: https://github.com/uber/baseweb/blob/main/package.json#L16
2. Can you add __tests__ for this component? (Unit tests and ubook stories can be added to this folder) You can start ubook dev with this script: https://github.com/uber/baseweb/blob/main/package.json#L17
3. Can you please bump the package version? Since it is a new component, I believe npm version minor is fine.

@hualf1995 Thanks! The PR has been updated.

1. Added images for both Light and Dark themes. Added stories screenshot as well.
2. Moved tests, but couldn't test them locally since test script & jest setup are not there. Do I miss something?
3. Done.

[hualf1995]

1. Can you try to run the documentation site app locally and attach a screenshot in the PR description? I feel you may need to add it to route to make it show up in doc site. You can use this script to develop on doc site: https://github.com/uber/baseweb/blob/main/package.json#L16
2. Can you add __tests__ for this component? (Unit tests and ubook stories can be added to this folder) You can start ubook dev with this script: https://github.com/uber/baseweb/blob/main/package.json#L17
3. Can you please bump the package version? Since it is a new component, I believe npm version minor is fine.

@hualf1995 Thanks! The PR has been updated.

1. Added images for both Light and Dark themes. Added stories screenshot as well.
2. Moved tests, but couldn't test them locally since test script & jest setup are not there. Do I miss something?
3. Done.

As per the test, I think you are right! Jest setup seems not available here.