JEP 413 Javadoc External Code Snippets do not work for JARs

# STR

## Given
1. A Java (18+) project with the following classes:
```java
package test;

/**
* Snippet file="test/SomeClass.java":
* {@snippet file="test/SomeClass.java" }
* -----------------
* Snippet file="SomeClassInDefaultPackage.java":
* {@snippet file="SomeClassInDefaultPackage.java" }
* -----------------
* Snippet file="./SomeClassInDefaultPackage.java":
* {@snippet file="./SomeClassInDefaultPackage.java" }
*/
public class Main {
}
```

```java
package test;

public class SomeClass {
public static void main(String[] args) {

}
}
```

```java
public class SomeClassInDefaultPackage {

}
```

in their corresponding directories (see attached file
[SnippetTest.zip](https://github.com/user-attachments/files/16581746/SnippetTest.zip)
). The JavaDoc view for Main.java displays:


2. Export the project to a JAR, *sources* and *binaries* together, and

3. Create another project and reference the exported JAR

4. Navigate to the JAR in the package explorer under "Referenced Libraries"

5. Navigate to test/Main.class and click on it

6. Show the JavaDoc view

## Expected

See image above.

## Actual


Start by reproducing the Javadoc view behavior with the attached SnippetTest.zip, following the steps for Main.java, SomeClass.java, and the exported JAR under Referenced Libraries. Investigate the Javadoc handling for external snippets when sources and binaries are packaged together; done means the referenced JAR displays the same snippets as the source project.

Written by the indexing model from the issue text.