Fix PyScript root component not hiding after render error

[Prachi-Gupta2808]

Description

Fixes the issue where a PyScript root component becomes unresponsive after an exception is raised during rendering.

Previously, the root model was updated using dict.update(), which could leave stale keys from the previous render. This caused the old DOM to remain visible instead of hiding the failed root component. The fix clears the existing root model before applying the latest update, ensuring the rendered state accurately reflects the current layout.

I have also added a regression test to verify that when a PyScript root component raises an exception during rendering, the component is removed from the page instead of leaving stale content behind.

Closes #1276

Checklist

Please update this checklist as you complete each item:

• Tests have been developed for bug fixes or new functionality.
• The changelog has been updated, if necessary.
• Documentation has been updated, if necessary.
• GitHub Issues closed by this PR have been linked.

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