[cowboyd]

Interactive terminal controls need focus, but focus is not inherently a keyboard concept and should not be reimplemented by every input element or framework adapter. A semantic Focus API provides one source of truth for the active node and lets controls declare focusability without knowing how users will navigate between them. Keeping this state in the middleware tree also makes focus available to custom element behavior such as layout, styling, and event handling.

Focus must remain valid as the Host tree changes. The first attached focusable element can become active automatically, traversal follows Host render order in both directions, and removing the focused subtree selects an appropriate replacement or returns to the host root. Focus changes also invalidate rendering so visual focus state is not delayed until another mutation.

This PR adds FocusApi, focus installation, focusability, direct focus assignment, and wrapping depth-first forward and reverse navigation. It handles initial focus, rejects invalid targets, repairs focus during subtree removal, and requests rendering when focus changes.

[pkg-pr-new]

• @examples/basic

  npm i https://pkg.pr.new/bombshell-dev/ui/@clack/ui@23
  

commit: 472a333

[cowboyd]

closing out in favor of a DOM based substrate. See #37