Test-Classpath ignores Runtime dependencies in Multi-Module-Projects

### Affected version

3.12.0

### Bug description

When creating a Test Javadoc report in a Multi-Module-Project, Runtime dependencies in modules are not properly considered when creating the classpath for test classes.

# Steps to Reproduce

You need just two POMs and one Java class.

Main Project **pom.xml**:
```xml

4.0.0
some.group.id
multi-module-parent
0.0.1-SNAPSHOT
pom

module

org.apache.maven.plugins
maven-javadoc-plugin
3.12.0

package

```
Module in **module/pom.xml**:
```xml

4.0.0

some.group.id
multi-module-parent
0.0.1-SNAPSHOT

module

net.minidev
json-smart
2.6.0
runtime

```
Test class in **src/main/java/example/Example.java**:
```java
package example;

import net.minidev.json.JSONArray;

public class Example {

void test() {
System.out.println(JSONArray.class);
}
}
```

# Expected Behavior

The project should compile fine and the report should be created normally.

# Actual Behavior

The project compiles fine, but the report fails with an error:

> [ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.12.1:site (default-site) on project multi-module-parent: Error generating maven-javadoc-plugin:3.12.0:test-aggregate report:
> [ERROR] Exit code: 1
> [ERROR] C:\devel\Eclipse\eclipse-2025-12\workspace\bar\module\src\test\java\example\Example.java:3: error: package net.minidev.json does not exist
> [ERROR] import net.minidev.json.JSONArray;

# Suspected Reason

According to the [Maven Documentation](https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html), the "Runtime" scope means that "Maven includes a dependency with this scope in the runtime and test classpaths, but not the compile classpath". This seems to work fine if it's a a single module, but maven-javadoc-plugin gets its wires crossed when determining the classpath for the actual report.

Reproduce the failure with the main pom.xml, module/pom.xml, and src/main/java/example/Example.java using the test-aggregate report. Trace how the report builds the test classpath for the multi-module project, then verify that the runtime dependency is included and the report completes without the missing-package error.

Written by the indexing model from the issue text.