Summary

This updates the @TempDir documentation examples to use standard JDK APIs instead of the internal ListWriter helper.

Changes

• Replace ListWriter usage in the Java TempDirectoryDemo
• Replace ListWriter usage in the Kotlin TempDirectoryDemo
• Remove the now-unused ListWriter helper

This keeps the examples self-contained and avoids referencing a non-JDK, non-JUnit utility type.

Fixes #5634.

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes