Plugins gain new UI focus/scroll and clock capabilities

What

• New ui.focus and ui.scroll hook events let a plugin request or commit keyboard focus onto an element it drew, and move or reveal scroll position within a transcript or pane it owns, with ownership checks so one plugin can't steal focus or scroll from another plugin's UI, and tracking of whether a person or the plugin itself initiated the action.
• The plugin-facing $.ui object gains ui.scroll (with to/in/block options) and ui.focus (with requestId/key), plus new closeOnEscape, holdToasts, and rows options on ui.open. A third new event, ui.blit, was also registered in the event-type system.
• A new $.clock plugin API adds now(), sleep(ms), after(ms, fn), and every(ms, fn), each validated to require non-negative millisecond counts and wired through cancellation/abort signals.

Why These additions give plugins finer control over their own UI (focus and scrolling, without interfering with other plugins) and a built-in way to schedule timed or repeating work, instead of needing to work around the host for either.