Close DeferredFileOutputStream to prevent FileNotFoundException on temp files

[Copilot]

Fixes #118. When using InputStreamTransformer with files exceeding the 5MB threshold, DeferredFileOutputStream creates temp files in /tmp but was never closed after writing. On Linux/macOS, subsequent reads fail with FileNotFoundException because the file isn't fully flushed to disk.

Changes

• PlexusIoFileResource.asDeferredStream(): Close dfos after copying transformed content to ensure temp file is flushed
• Deferred constructor: Close dfos after copying to ensure temp file is accessible for subsequent reads
• PlexusIoFileResourceDeferredTest: Add tests covering multiple reads, large files (>5MB threshold), and small files (<5MB)

The existing cleanup logic (deleting temp file on InputStream close) remains unchanged.

Original prompt

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This section details on the original issue you should resolve

<issue_title>plexus-io:3.3.0 error: tmp/maven-metadata-local.xml3261144141794286831.tmp (No such file or directory)</issue_title>
<issue_description>I upgrade plexus-io from 3.2.0 to 3.3.0 because of the CVE issue, and get error as:
[ERROR] Failed to execute goal org.apache.karaf.tooling:karaf-maven-plugin:4.2.7:kar (create-kar) on project testRoute-feature: Failed to create archive: Problem creating jar: Execution exception: java.io.FileNotFoundException: /tmp/maven-metadata-local.xml11604840448228358901.tmp (No such file or directory) -> [Help 1]
How to reproduce?
extract testRoute.zip,
execute in testRoute folder.
mvn -X -B package -llr -Dmaven.test.skip=true -Dmaven.main.skip=true

Note. This error only happens in Linux/mac os. details error see
mvn.log
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes plexus-io:3.3.0 error: tmp/maven-metadata-local.xml3261144141794286831.tmp (No such file or directory) #118

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[slachiewicz]

@copilot use try with resources to close streams always