fix: ytsync — classify youtu.be/<id> short links as videos; sync tools-docs thumbnail flag

DOC/AGENT_Context_Project.md

@@ -605,7 +605,7 @@ Use conventional prefixes: `feat:`, `fix:`, `docs:`, `refactor:`, `chore:`
 | `bin/pos-media-mp3` | 86 | Download audio as MP3 (yt-dlp) |
 | `bin/pos-media-mp4` | 132 | Download video as MP4 (smart/interactive format select) |
 | `bin/pos-media-sync` | 164 | Incremental Music → USB sync (mp3/mp4, add/update only) |
-| `bin/pos-media-ytsync` | 1180 | Incrementally sync YouTube channels/playlists into ~/Videos |
+| `bin/pos-media-ytsync` | 1190 | Incrementally sync YouTube channels/playlists into ~/Videos |
 | `bin/pos-network-checkport` | 496 | Check TCP/UDP port reachability (nmap, or bash/nc fallback) + local interface view |
 | `bin/pos-network-download` | 951 | aria2 RPC daemon + queue control (add/torrent/metalink, watch, limits) |
 | `bin/pos-network-hotspot` | 93 | Wi-Fi hotspot via create_ap + wihotspot-gui |

DOC/POS.md

@@ -214,7 +214,8 @@ The standalone `vbox` command still works and forwards to `pos docker vbox` (see
 
 A watch link carrying **both** `?v=` and `&list=` downloads only that single video
 (`--no-playlist`) — nobody accidentally backfills a 500-video playlist from a watch
-link; a pure playlist link becomes a tracked playlist source with numbered
+link; `youtu.be/<id>` short links count as watch links too. A pure playlist link
+becomes a tracked playlist source with numbered
 `<NNN> - <title>.mp4` files. `pos media ytsync remove <name>` stops tracking but
 keeps the downloaded files AND the archive — re-adding the same source later
 resumes incrementally instead of re-downloading. Members-only/age-gated videos are

DOC/howto/media.md

@@ -183,7 +183,7 @@ Where files land:
 Notes:
 
 - A watch link with **both** `?v=` and `&list=` downloads only that single video,
-  never the whole playlist.
+  never the whole playlist; `youtu.be/<id>` short links count as watch links too.
 - Retitled/renamed videos keep their local filenames (the archive is keyed by video
   id); inserting a video mid-playlist shifts future numbering only.
 - Members-only / age-gated videos are skipped with a count ("N videos require