fix: invalidate node maps when nodes change in-between paints #5694.

[DustinMackintosh]

Description
This fixes an editor crash where the user types quickly after earlier nodes have been added, split or deleted, but the node maps have not yet been regenerated on React render.

Issue
Fixes: (link to issue)

Example
Recording (from issue linked above)
https://github.com/user-attachments/assets/a68453b1-df47-4324-a542-9313569958ca

Sandbox (from issue linked above)
https://codesandbox.io/s/slate-selection-change-repro-ztssmp

Context
The NODE_TO_INDEX WeakMap is built on each React render as part of the useChildren hook. Both onDOMBeforeInput and onDOMSelectionChange use these maps to set the selection. This change introduces a new WeakMap called IS_NODE_MAP_DIRTY to track whether the underlying nodes have changed (eg: remove_node or insert_node), allowing those methods to skip attempts to setSelection that could crash the component.

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Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

🦋 Changeset detected

Latest commit: dcebdba

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slate-react	Patch

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[Calyhre]

We have the same issue on our side, and this patch seems to solve it 👍

[dylans]

Ok, this looks reasonable. Obviously if it causes any major regressions we may need to revert it.