Fix/container gc retention

[edwardwkrohne]

📝 Summary

Closes #9880

Widgets created as

get_state, set_state = mo.state(False)
wgt = mo.ui.checkbox(on_change=set_state).style()
wgt

would never fire their set_state methods. The issue is that style returns

    return Html(h.div(children=as_dom_node(item).text, style=style_str))

which drops the actual python object item, preventing the corresponding frontend ui object from actually interacting with the backend.

Now, style is a class that derives from a new class ContainerHtml, which explicitly contains strong references to a list of children to prevent them from being garbage collected. The offending code survives as

    def _build_text(self) -> str:
        return h.div(children=self._children[0].text, style=self._style_str)

which uses the explicitly stored child self._children[0] instead of a local. Similar treatment has been given to accordion, callout, carousel, tabs, and sidebar, all of which could potentially drop their children by converting to text and losing the original.

tabs was slightly different in that it was already a UIElement, which would have been incompatible with the implementation of the new ContainerHtml class, so it was modified to explicitly store its own children.

sidebar was reparented to ContainerHtml and stores its children that way.

_BlockWrapped was also reparented to ContainerHtml.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jun 18, 2026 4:00am

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