Alt key doesn't work in Netbeans cygwin Terminal

### Apache NetBeans version

Apache NetBeans 15

### What happened

I use cygwin terminal to have a CLI in NetBenas, it's really useful but when I try to use some ASCII characters I usually type the ASCII code but the Alt key doesn't seem to work.

I thought it was a cygwin issue, but when I open the cygwin terminal directly outside Netbeans, the Alt Key does work.

### How to reproduce

* Install cygwin in Netbeans to use terminal
* Try to type any ASCII character using it's ASCII code

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

No / Don't know

### Operating System

Windows 10

### JDK

17

### Apache NetBeans packaging

Apache NetBeans provided installer

### Anything else

_No response_

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

No

### Code of Conduct

Yes

Reproduce the issue on Windows 10 with Apache NetBeans 15, JDK 17, and a Cygwin terminal configured inside NetBeans, then compare Alt-key input with Cygwin opened outside NetBeans. Trace the NetBeans terminal integration involved in keyboard handling. Done means ASCII characters entered with Alt codes work in the embedded terminal as they do in the standalone Cygwin terminal.

Written by the indexing model from the issue text.