fix: firefox input (#14315)

fix #14296 
fix #14289

#### PR Dependency Tree


* **PR #14315** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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## Summary by CodeRabbit

* **Bug Fixes**
* Improved inline editor stability for selection edge cases and
beforeinput handling, with better recovery and native-input protection.
* Fixed potential crashes when deleting with selections outside the
editor bounds, including Firefox-specific scenarios.

* **Tests**
* Added unit tests covering beforeinput behavior and added Firefox
end-to-end regression tests.

* **Chores**
  * Reduced CI test parallelism to streamline pipeline.

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