Migrate the LiveStream 054 batch (34 files) #30

• Series: Livestream
• Files: 34
• Estimated time: ~90 minutes
• Labels: good-first-issue, i16-translations

LiveStream_054 ("Mathematical Foundations for a Compositional Account of the Bayesian Brain", Smithe) still holds 34 files in three stems: "…054.0…" → HK9ZkbxieLY, "ls054 1 …" → fzFDvJhrn0U, "054.2…" → GfImcptiLsY. Includes one en(ie) file (treat as en).

Scope (from the triage doc, Part A):

• Item Livestream/LiveStream_054
  • 11 files, stem Active Inference LiveStream 054.0 ~ Compositional Account of the Bayesian Brain - Smithe → target translations/HK9ZkbxieLY.<bcp47>.srt
  • 11 files, stem Active Inference LiveStream 054.2 ~ “...Compositional Account of the Bayesian Brain” (Smithe) → target translations/GfImcptiLsY.<bcp47>.srt
  • 12 files, stem ls054 1 Compositional Account of the Bayesian Brain Smithe → target translations/fzFDvJhrn0U.<bcp47>.srt

Read first: docs/volunteer-transcript-tasks.md —
sections "The 30-minute task (per file)" and "Exact command pattern".

Steps, per file:

1. Verify the guessed video_id in the item's metadata.json + a YouTube spot-check of the part.
2. Confirm the language by opening the .srt (normalize legacy codes per the migration map).
3. Move with the two-step git mv into translations/<video_id>.<bcp47>.srt.
4. Append the original repo-relative path to the destination item's metadata.json previous_paths.
5. One path-scoped commit per item: translations(<series>): migrate <N> legacy files (I16 triage).

Acceptance criteria:

• every listed file moved (or deleted, if byte-identical to an already-migrated target) with previous_paths recorded
• no listed file remains in the item's Translations/ folder; empty Translations/ and translations_tmp/ removed
• spot-checked target files open as valid subtitles and match the verified part/language