fix(youtube): preserve playlist video uploaders

[Priveetee]

Found while working on TypeType public YouTube playlist support:

TypeType-Video/TypeType#106

Summary

While working on public YouTube playlists for TypeType, I found that mixed YouTube playlists can report the playlist owner as the uploader for every video on the initial playlist page.

This fixes YouTube playlist lockupViewModel entries overriding the per-video uploader with the playlist uploader whenever the playlist uploader fallback is available.

Problem

The playlist page can expose the correct uploader per video through YoutubeLockupStreamInfoItemExtractor.

However, YoutubePlaylistExtractor currently wraps lockup video items and returns the playlist uploader whenever fallbackName / fallbackUrl exists:

video uploader = playlist uploader

Observed on a public YouTube playlist:

https://www.youtube.com/playlist?list=PLMC9KNkIncKtPzgY-5rmhvj7fax8fdxoj

Before this change, the first page returned different videos with the same uploader:

Lady Gaga, Bruno Mars - Die With A Smile | ka-Redlist - Just Hits
DJ Snake - Let Me Love You | ka-Redlist - Just Hits
Michael Jackson - Thriller | ka-Redlist - Just Hits

Changes

• Keep the uploader parsed from each YoutubeLockupStreamInfoItemExtractor when available.
• Use the playlist uploader name/url only as a fallback when the video uploader cannot be parsed.
• Keep the change limited to YouTube playlist lockup video items.

Validation

• JAVA_HOME=/usr/lib/jvm/java-25-openjdk ./gradlew :extractor:compileJava
• Local extractor smoke against:

https://www.youtube.com/playlist?list=PLMC9KNkIncKtPzgY-5rmhvj7fax8fdxoj

After:

playlist=ka-Redlist - Just Hits
Lady Gaga, Bruno Mars - Die With A Smile | Lady Gaga
DJ Snake - Let Me Love You | DJ Snake
Michael Jackson - Thriller | Michael Jackson
ROSÉ & Bruno Mars - APT. | ROSÉ
Madison Beer - lovergirl | Madison Beer

Notes

This keeps the playlist uploader fallback behavior for cases where YouTube does not expose a video uploader, but avoids replacing valid per-video uploader metadata.