Keep work in progress safer through editing interruptions

We strengthened the editor around the moments when a page is still loading, a collaborative connection is interrupted, or a recovery is required.

• Meaningful content is protected while the editor starts: closing, saving, or publishing before the editor is fully ready can no longer replace an existing post with an empty state.
• Temporary interruptions recover more safely: the editor preserves current work, reconnects automatically when it can, and shows a clear recovery path when a reload is needed.
• Unsaved post settings survive necessary reloads: drafts in JSON-LD and Custom Code are restored without automatically replacing newer values that have already been saved.
• Background activity stays out of the way: automatic version snapshots pause after a background connection is cleaned up, and confirmed saves stay correctly tracked as the editor re-renders.