v0.56.1

Test and CI reliability only. The published library is unchanged from 0.56.0.

The component test job flaked in CI on the editor's heavier pages (the CairnAdmin edit view and the insert dialog) because the editor's per-browser preferences live in localStorage and nothing cleared it between tests, so a leaked zen preference could hide the toolbar a later test waited for. localStorage is now isolated before each component test, with a regression guard, plus a retry on the browser test project and steadier waits in the insert-dialog tests.

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