Watched object in debug session cannot be expanded

### Apache NetBeans version

Apache NetBeans 29

### What happened

The watched object cannot be expanded in the table, even its type is a list.

### Language / Project Type / NetBeans Component

Java application with Ant

### How to reproduce

1. Enter the following watch: `ManagementFactory.getRuntimeMXBean().getBootClassPath()`
2. Change the watched expression to: `ManagementFactory.getRuntimeMXBean().getInputArguments()`

Even the result is a list, the expansion is not possible. If you enter the second watch directly as a new watch, the expansion is available.

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

No / Don't know

### Operating System

Ubuntu 24.04

### JDK

Bundled JDK 25

### Apache NetBeans packaging

Community provided installer

### Anything else

_No response_

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

No

Reproduce the problem in an Apache NetBeans Java application by changing the watch from getBootClassPath() to getInputArguments(), then compare it with adding getInputArguments() as a new watch. Trace the debugger's watch-expression evaluation and expansion handling. Done means the changed watched expression can be expanded when its result is a list, matching the behavior of a newly added watch.

Written by the indexing model from the issue text.