CLASS_FILTER in JarAnalyzer rejects underscores in Java class names

In `JarAnalyzer.java:38`:

```java
private static final Pattern CLASS_FILTER = Pattern.compile("[A-Za-z0-9]*\\\\.class$");
```

The character class `[A-Za-z0-9]` excludes `_` (underscore), which is a legal character in Java class names. Any class like `My_Helper.class`, `some_test.class`, or `UPPER_CASE.class` inside the JAR is silently ignored and never analyzed. This causes incomplete class discovery, potentially missing packages, imports, and leading to incorrect JDK revision detection.

**Fix**: Add `_` to the character class: `[A-Za-z0-9_]*\\\\.class$`

Open JarAnalyzer.java and inspect the CLASS_FILTER declaration at line 38. Verify the filter against JAR entries whose class names contain underscores, such as My_Helper.class. Done means those classes are discovered and analyzed instead of being silently ignored.

Written by the indexing model from the issue text.