[tiensonqin]

Summary

• Add ?on_focus_within:(bool -> unit) to row, column and box so a row-owned signal can keep a comment toolbar visible while a body link or reaction has focus. FocusWithinEnabled defaults to absent/off; observation never makes the container focusable.
• Web coalesces node-local focusin/focusout checks with retained-node teardown. MyGo reads committed Handle.FocusWithin(c) in its existing event queue after descendant autofocus, then publishes one initial snapshot and distinct changes, including false on disabled/inert transitions. SwiftUI, Kotlin, Generic and mobile raw-wire hosts reject opt-in rather than silently omitting events.
• MyGo rejects enabled observation on box display=contents at both OCaml and raw-wire admission, preserving transparent-anchor rendering without promising an absent native focus surface. Observe a real container instead; Web retains DOM-subtree observation for that combination.
• Regenerate wire/MyGo schemas and document migration. No SDK, Dune, dependency or storage changes.

Checked: OCaml @all/@runtest, schema generation and tests, Web build/unit tests, Go tests (including race)/vet and cross-builds, Swift wire build/test and Android :lui:testDebugUnitTest. Added red-green regressions for committed autofocus snapshots and transparent-box admission. No GUI validation in this slice.

Link to Devin session: https://app.devin.ai/sessions/71c38037048d4f76b7cef6d695621ef6
Open in Devin Desktop: https://app.devin.ai/desktop/session/71c38037048d4f76b7cef6d695621ef6?variant=devin
Requested by: @tiensonqin

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring