The MVEB+ video task set had inconsistent and partially-wrong `domains`
tags. Issues fixed:

- MSR-VTT had no domain tags at all (empty list). Now tagged ["Web"].
- AVMeme-Exam was tagged with "Music" (it's internet memes, not music
  content). Now ["Entertainment", "Web"].
- AudioCaps_AV was tagged "Encyclopaedic" (it's audio captioning). Now
  ["AudioScene", "Web"].
- VGGSound was tagged just ["Web"] despite being audio-visual events.
  Now ["AudioScene", "Web"]. Same fix for VGGSound_AV_RETRIEVAL.
- AV-SpeakerBench was tagged ("Web") on the base task and ("Spoken")
  on the PC variant --- same source data, inconsistent tags. Unified
  to ("Spoken").
- WorldSense_1min was over-tagged with Entertainment+Music in some
  files and just ["Web"] in others. Unified to ["AudioScene", "Scene",
  "Web"].
- Several datasets tagged "Spoken" without speech-driven content
  (DiDeMo, MSVD, ActivityNetCaptions, VATEX, panda-70m, TUNA-Bench).
  Removed the Spoken tag from those.
- AVE-Dataset clustering tasks tagged with ["Music", "Scene", "Spoken"]
  (clearly wrong). Now aligned with the rest of AVE-Dataset:
  ["AudioScene", "Web"].
- MELD was tagged just ["Entertainment"] across base and clustering
  variants; MELD is the Friends sitcom, so dialogue is central.
  Added "Spoken" -> ["Entertainment", "Spoken"].
- UCF101 missing "Sport" tag. UCF101 has substantial Sport content.
  Now ["Scene", "Sport", "Web"].
- Human-Animal-Cartoon missing "Entertainment" tag despite the cartoon
  domain. Now ["Entertainment", "Scene", "Web"].
- PerceptionTest missing "Scene" tag despite being a scene-perception
  benchmark. Now ["Scene", "Web"].
- Video-MME missing "Spoken" tag despite the narration-heavy content.
  Now ["Spoken", "Web"].
- HMDB51 missing "Web" tag (sourced largely from web video). Now
  ["Scene", "Web"].
- VideoCon, Vinoground (zachz/*) missing "Web" tag. Added.
- RAVDESS tag list kept at ["Spoken"] (speech-emotion primary).
- AVQA tag list extended with "AudioScene" (it's an audio-visual QA
  benchmark).

All 50 unique source datasets across 184 video tasks now have
consistent, non-empty domain tags. Verified by re-importing every
task: 184 tasks load cleanly.

Tags use only the existing TaskDomain Literal vocabulary in
task_metadata.py; no new domains added.

…datasets

Adds 5 video content domains to TaskDomain (Activity, Instructional,
Egocentric, Nature, Animation) and re-tags datasets that were mislabeled
or under-characterized, so the domain set actually reflects benchmark
content:

- Action recognition (Kinetics-400/600/700, HMDB51, UCF101, SSv2,
  ActivityNet, VATEX, NExT-QA, Vinoground, VideoCon) -> Activity
  (was the catch-all "Scene", which means visual place/setting).
- Breakfast, YouCook2 -> Instructional (cooking / how-to).
- Diving48 -> Activity + Sport.
- EgoSchema -> Egocentric (was bare "Web").
- Human-Animal-Cartoon -> Activity + Animation + Nature.
- AVMeme-Exam -> + Social (internet memes).
- PerceptionTest -> drop misapplied "Scene".

Scene is now reserved for genuine visual-scene content (WorldSense).
All 184 video tasks load; every domain validates against TaskDomain.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>