wiki: add Plex 4K codec guide and mdadm USB recovery; update yt-dlp, indexes

New articles:
- 04-streaming/plex/plex-4k-codec-compatibility.md
- 05-troubleshooting/storage/mdadm-usb-hub-disconnect-recovery.md

Updated:
- yt-dlp.md: Plex section and config reflect new HEVC auto-convert workflow
- SUMMARY.md, index.md, README.md, section indexes: 39 → 41 articles
- MajorWiki-Deploy-Status.md: count + date

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

04-streaming/index.md

@@ -5,3 +5,7 @@ Guides for live streaming and podcast production, with a focus on OBS Studio.
 ## OBS Studio
 
 - [OBS Studio Setup & Encoding](obs/obs-studio-setup-encoding.md)
+
+## Plex
+
+- [Plex 4K Codec Compatibility (Apple TV)](plex/plex-4k-codec-compatibility.md)