Undo and Redo are very slow

### Apache NetBeans version

Apache NetBeans 20

### What happened

Undo and Redo (Ctrl+X and Ctrl+Y) are extremely slow.

I've tried deactivating plugins, cleaning the cache, and reducing the project size to the minimum - but it didn't help.

Undo and Redo are normal after opening the IDE, but it feels the longer it is open, the slower the Undo and Redo.

### Language / Project Type / NetBeans Component

PHP

### How to reproduce

Undo and Redo (Ctrl+X and Ctrl+Y). Maybe wait a couple of hours after opening the IDE.

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Windows 11

### JDK

19.0.1; Java HotSpot(TM) 64-Bit Server VM 19.0.1+10-21

### Apache NetBeans packaging

Apache NetBeans provided installer

### Anything else

_No response_

### Are you willing to submit a pull request?

No

Start by reproducing Undo and Redo with Ctrl+X and Ctrl+Y in a PHP project on NetBeans 20, comparing behavior immediately after startup with behavior after several hours. No source file or test is identified, so the investigation must first locate the editor undo/redo path and measure the slowdown; done means identifying the cause and verifying responsive undo and redo.

Written by the indexing model from the issue text.