Greatly reduced offer in code completion

### Apache NetBeans version

Apache NetBeans 30

### What happened

Code completion is greatly reduced under some circumstances in java application project using **Java platform 1.8**.

### Language / Project Type / NetBeans Component

Java with Ant

### How to reproduce

For example, for class `javax.net.SocketFactory`:

1. Typing "Socket" and invoking code completion provides the full result:

>

2. However, if you type "SocketFa" and then invoke code completion, the result is just the `Unsafe` class:

It happens only when using **Java platform 1.8** (distribution is "zulu8.90.0.19-ca-jdk8.0.472-linux_x64").
With JDK 11, 21, 25 and 26, the behavior is OK:

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

Apache NetBeans 29

### Operating System

Ubuntu 24.04

### JDK

JDK 26 bundled with NetBeans

### Apache NetBeans packaging

Community provided installer

### Anything else

_No response_

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

No

Start by reproducing the completion behavior in Apache NetBeans 30 with a Java with Ant project using Java platform 1.8, comparing "Socket" and "SocketFa" for javax.net.SocketFactory. Compare the same steps on JDK 11, 21, 25, and 26, then trace the code-completion entry point to identify the Java 8-specific difference. Done means completing the longer prefix returns the expected relevant results without regressing other JDK versions.

Written by the indexing model from the issue text.