OptionaleventBus: CompatEventBusWhether a usable container was resolved (requires a DOM).
The mounted element, when mount has completed.
Removes the mounted element from the container.
Ensures the injected web-component kit is registered and the element is
mounted into the container. Returns the element, or undefined when no
DOM / container / kit is available (headless shims, or an application
that never called registerHonuaWidgetKit).
A container was supplied but no kit was registered — the "migrated app comes up blank" case — is the one failure worth being loud about, so it emits the one-time diagnostic. Headless usage (no DOM, no container) stays silent: that is a legitimate state-model-only mode, not a mistake.
Mounts (when needed) and applies assign to the element. Fire-and-forget
friendly: shims call void host.update(...) from synchronous refresh
paths.
Bus the owning shim publishes on. Optional so headless / standalone construction keeps working; when omitted the missing-kit diagnostic still reaches the console.