What?

Fix stale CRDT document being persisted during save when real-time collaboration is enabled.

Why?

When sync is enabled, Y.Doc updates are deferred via setTimeout(0) for performance. saveEntityRecord calls __unstablePrePersist to serialize the CRDT document, but it was doing so without yielding to the event loop first. This meant the serialized _crdt_document was stale — it didn't include the most recent Y.Doc updates. On reload, _applyPersistedCrdtDoc detected the mismatch and triggered an unnecessary reconciliation save.

How?

• Add a setTimeout(0) yield inside saveEntityRecord before calling __unstablePrePersist, only when syncConfig is present. This flushes any pending deferred Y.Doc updates before serialization.
• Extract repeated waitForFunction/evaluate blocks from the collaboration persistence E2E tests into three reusable CollaborationUtils helpers: waitForEntityReady, waitForEntityReadyAndSaveSettled, and getCrdtDocument.
• Add a new E2E test (persisted CRDT document matches content after save and reload) that verifies the CRDT document is identical before and after a save-reload cycle.

Testing Instructions

1. Enable real-time collaboration in Settings → Writing.
2. Create a new draft post with a paragraph block.
3. Type some content.
4. Open the browser Network tab and filter by posts/:id to see REST API calls to wp/v2/posts/:id.

On trunk (before this PR):

5. Click Publish — observe a POST request to posts/:id.
6. Reload the page.
7. A second POST request to posts/:id fires automatically after reload — this is the unnecessary reconciliation save caused by the stale CRDT document.

On this branch (after this PR):

5. Click Publish — observe a POST request to posts/:id.
6. Reload the page.
7. No additional POST request to posts/:id fires — the persisted CRDT document is up-to-date so no reconciliation save is triggered.

Automated

npx playwright test --config test/e2e/playwright.config.ts test/e2e/specs/editor/collaboration/collaboration-persistence.spec.ts

All 3 tests should pass. The third test (persisted CRDT document matches content after save and reload) fails without the actions.js fix.

Testing Instructions for Keyboard

N/A — no UI changes.