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§01
Contract
Semantics first
Anatomy
Renders the primary region as a neutral div and the rail as aside; visual and DOM order match railPosition.
Consumer classes, styles, and data attributes may extend the surface, but required roles, IDs, relationships, and handlers remain owned by the component.
Keyboard
No custom keyboard contract; interactive content in the main and rail uses document order.
§02
Public surface
API & styling
Props
id
Explicit IDs override stable generated IDs.
class / style
Consumer additions compose with required styles.
ref
Element or callback where focus control is expected.
children
Typed content; raw HTML strings are never rendered.
Slots & events
children
Primary content slot.
onChange
Typed value plus a small reason object when state changes.
There is no stable predecessor for this explicit compiled subpath. The v1 compatibility layer remains tested separately; visual and API diffs begin with the next prerelease.