The feedpak spec defines keys.json (instrument-independent key/scale-change
track, §7.7) but core never loaded it. Add it, mirroring the song_timeline /
drum_tab side-file pattern:
- lib/sloppak.py: LoadedSloppak gains a `keys` field; a permissive loader reads
the manifest `keys:` key, path-safety-checks it, and stores a SANITIZED
{version, events:[{t, key, scale?}]} — finite non-bool t (bad-t events dropped,
not rewritten to 0), non-empty string key, optional string scale, sorted.
Missing / unreadable / malformed -> None, never fatal. int-only version
(a float/NaN version can't abort the load).
- server.py: stream a `keys` highway-WS message when present + a `has_keys`
song_info flag so a consumer can light up a key/scale display.
Renderer/HUD surfacing is a thin follow-up; this lands the data plumbing so
the highway, plugins, and the upcoming scale-degree (`sd`) annotation can read
the active key/mode from the WS.
Codex-reviewed (2 rounds: version-int-coercion + bad-t-drop hardening); clean.
+7 loader tests (happy path, absent/permissive variants, sanitize/sort,
non-int-version no-abort). 150 sloppak/load tests pass.
Closes#525. Part of got-feedback/feedback#334.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
