Core read, served, and depended on `original_audio:` — a top-level manifest key
this repo invented in #583 that the feedpak spec never defined. The format
already had a home for the pre-separation mixdown: it is a stem. feedpak 1.15.0
(feedpak-spec#53) RESERVES the id `full` for it, so read it from there.
The key existed to work around a bug in our own reader. The packer's comment
said so plainly: "we must NOT list the full mix as a playable stem — the player
sums every entry in `stems` and does not gate playback on `default`, so a listed
full mix plays on top of the stems". Faced with a reader that would double the
song, the packer put the mixdown outside `stems` and invented a key to point at
it. The fix belongs in the reader, and that is what this is.
load_song() now partitions the stem list: `full` comes out as
LoadedSloppak.full_mix, the instruments stay in .stems. Nothing that sums stems
or draws one fader per stem can see the mixdown, so retaining it is safe — which
is what lets the packer put it where the format says it goes.
- ws_highway: `song_info` gains full_mix_url / has_full_mix. The old
original_audio_url / has_original_audio remain as deprecated aliases for one
release so an older stems plugin keeps working (#945).
- `stems` on the wire, and stem_ids / stem_count in the library index, are now
INSTRUMENT stems only — a separated pack that retains its mixdown no longer
advertises a bogus "full" chip or an inflated stem count.
- enrichment: fingerprint against the mixdown wherever it lives. This widens
coverage — _song_audio_file() previously returned None for any pack without
the invented key, so fingerprinting silently did nothing for nearly every pack.
- sloppak: `original_audio:` is still READ as a deprecated fallback, because
every pack in the wild carries it and would otherwise lose its pristine mix.
tools/migrate_full_mix_stem.py rewrites those packs into the spec shape
(original/full.ogg -> stems/full.ogg, add the `full` stem at default:off, drop
the key); the fallback and the aliases die with #945.
The spec gate keeps the debt honest: the grandfather entry now tracks #945, and
the gate fails if it goes stale.
Verified: spec gate OK (4/4, incl. ingesting the spec's new example pack that
retains `full`); 2493 python tests, 995 js tests; migrator round-tripped over
real packs from the library and the results pass the spec's reference validator.
