fix: #3608868 Move remote-video oEmbed demo content out of the auto-applied install path

Two remote-video demo media entities (content/media/remote-video--remote-vimeo-video.yml, content/media/remote-video--remote-youtube-video.yml) made a live external oEmbed validation call during recipe content import, which has no retry and a short timeout — causing intermittent drush site:install failures (observed: YouTube oEmbed DNS timeout, Vimeo 'no matching oEmbed provider' twice), even though the videos themselves and the provider APIs are live and reachable.

Moves both media entities out of the main auto-applied recipe into a new, optional remote_video_samples/ sub-recipe. The main Varbase Media Assets recipe no longer depends on any live network call during install — it installs fast and reliably every time. The remote-video samples remain available on demand via drush recipe <path-to-remote_video_samples> once network access is confirmed, documented in the sub-recipe's own description and this project's README.

Related issue: #3608868 (references prior #3580300, which fixed a dead-video variant of this content and is a separate, already-closed problem).

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This changeset was produced with AI assistance (Claude Code). Per the Drupal AI-generated contribution policy, it has been reviewed by a human before submission.

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