fix: prevent IME preedit overflow in mind map node editor (#14520)

## Summary

Update the edgeless shape text editor to resize mind map node text
bounds while IME composition is in progress.

## Changes

- listen to `compositionupdate` on the inline editor container
- trigger `_updateElementWH()` on `compositionupdate` and
`compositionend`
- keep text box dimensions in sync before composition is committed

## Testing

- Not run locally: `pnpm` is not available in this environment, so
package build/tests could not be executed here.

Fixes #11515


<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **Bug Fixes**
* Editor mounting tolerates missing/null elements and validates input to
avoid errors.
* Text creation/update consistently targets the refreshed element to
prevent mismatches.
* Inline editor listens for IME composition events and schedules
layout/size recalculation (with proper cleanup) so sizing stays in sync.

* **Tests**
* Added an integration test verifying layout/size updates during IME
composition events.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>
Co-authored-by: DarkSky <darksky2048@gmail.com>