[Epic] feedpak format extension, enrichment & editor authoring

[byrongamatos]

Umbrella for extending the feedpak format and tooling so authored musical data is richer, renderable, and editable end-to-end. The format is governed by the public spec got-feedback/feedpak-spec (v1.2.0); changes there go through the FEP process (vendor-neutral, additive/MINOR). Implementation lives in feedback (core + bundled plugins/highway_3d/ + 2D static/highway.js) and the feedback-plugin-* repos.

Principles

• Definition of done = spec/impl carries it + a renderer draws it + the editor authors it. No converter-only dead data.
• Chart vs state: feedpak holds the authored chart only. Progress/session/loop/timbre stay in app stores.
• Already in the spec: centOffset, sections/beats, keys.json (= key/mode regions), song_timeline.json tempos/time-signatures, per-chart tempos.

Editor + render + import track — ✅ COMPLETE

• [E0] Editor chord-model foundation: preserve authored template metadata across save feedBack-plugin-editor#3 — E0 chord-model foundation (fixes GP5 name-loss) — PR bug: Auto-mode under splitscreen — add per-panel matchesArrangement evaluation #6
• [E1] Chord inspector: author chord name + per-string fingering feedBack-plugin-editor#4 — E1 chord inspector (name + fingering) — PR feature: integrate per-stem volume sliders into the mixer popover #7
• [E2] Handshape / arpeggio (chord-shape) region authoring feedBack-plugin-editor#5 — E2 handshape / arpeggio authoring — PR feat: shared audio analyser API for plugins (Web Audio AnalyserNode) #10 + feat: read .wem files direct from folders #11
• GP import: extract chord-diagram fingerings (GP5/GP8) + GP8 chord names #335 — E3 GP import enrichment (chord-diagram fingerings + GP8 names) — PR feat(gp): extract GP chord-diagram fingerings + GP8 chord names (E3) #522 + fix(gp): GP5 chord enrichment — diagram-match gate + decoupled name/fingers (E3 follow-up) #523
• 2D highway: render unpitched slides (slu) #336 — Item 1 2D highway: render unpitched slides (slu) — PR feat(highway-2d): render unpitched slides (slu) #524
• 3D anchor highlight, 3D slu, arp framing were already in current core.

Core backlog — consume what the 1.2.0 spec already defines (no FEP needed)

• feat(core): consume keys.json — song-level key/scale track (loader + WS + display) #525 — consume keys.json (loader + WS) — unblocks sd — PR feat(core): consume keys.json — song-level key/scale track (loader + WS) #528
• feat(core): consume song_timeline tempos + time_signatures + per-chart tempos (feedpak 1.2.0) #526 — consume song_timeline tempos/time-signatures + per-chart tempos — PR feat(core): consume song_timeline tempos + time_signatures + per-chart tempos (1.2.0) #529
• chore(core): adopt feedpak_version (read on load + emit on write) per spec §4 #527 — adopt feedpak_version — PR feat(core): adopt feedpak_version — read on load + stamp on manifest writes (§4) #530

Format FEPs (public spec repo; coordinate with topkoa/mogul)

• Bend curves (bnv + bt) — spec ✅ merged (feedpak-spec#17, 1.4.0); impl ✅ complete: core wire + GP5/GP8 import (feat(core): per-note bend shape (bt + bnv) — wire + GP import (PR-A) #531) · 2D/3D highway render (feat(highway): render per-note bend curve (bnv) on 2D + 3D (PR-B) #532) · editor authoring (feedback-plugin-editor#13); Codex follow-up fixes ✅ merged (core fix(bend): GP8 short-bend curve loss + 2D curve timing + 3D bnv gating (Codex follow-ups) #535: GP8 short-bend + 2D/3D bnv gating · editor Keyboard shortcuts needed for all sliders #15: bn/bnv desync)
• Teaching marks (fg/ch/sd) — spec ✅ merged (feedpak-spec#21, 1.5.0; FEP Bundle Tailwind #19) + honesty rule. Impl ✅ complete: core wire+GP fingering import+sd derive (feat(core): teaching marks fg/ch/sd — wire + GP import + sd derivation (§6.2.2) #536) · 2D/3D highway render (feat(highway): render teaching marks fg/ch/sd on 2D + 3D (§6.2.2) #538) · editor authoring (editor#16). Review-loop fixes: range-guard (editor#17), fg hideable toggle (fix(highway): make fret-hand finger (fg) hints hideable, default on (review follow-up to #538) #539), undo-on-save reset (editor#19 + atomic-rebuild hardening Address AppImage packaging warnings #20, closes editor#18)
• Per-chord harmony (FEP Why two DLC folder settings? #24) — ✅ COMPLETE end-to-end. Spec: fn+voicing (MIDI record: capture velocity (requires sloppak wire-format change) #25, 1.7.0) + caged+guideTones (MIDI record: Quantize 1/16 (and other grids) on a recorded arrangement #27, 1.8.0). Impl: core wire feat(core): carry chord harmony fn + template voicing on the wire (§6.3.1, §6.6) #540/feat(song): wire caged + guideTones chord-template fields (§6.6) #544 (+ emit-guard fix(song): sanitize caged + guideTones on emit, not just decode (#544 follow-up) #547) · 2D/3D render feat(highway): render chord harmony fn.rn + voicing on 2D + 3D (§6.3.1, §6.6) #541/feat(highway): render caged + guideTones teaching labels (§6.6) #545 · editor authoring feature: Replace sliders with number entry+popup #16/MIDI record: capture velocity (requires sloppak wire-format change) #25 (+ fn-rides-notes Reinitialize input/output options without restart #22, range-guards Plugins should always run in a read-only filesystem #17)
• Song-level harmony track (intended progression) — FEP RFC open (feedpak-spec#28): proposed harmony.json sibling side-file (time-ordered {t,root,quality,rn?,bass?} events); resolves the fn as-played/intended boundary (Why two DLC folder settings? #24 Q5); awaiting maintainer input on keys.json-vs-new-file + root encoding before a spec PR. Foundation for ↓
• (dependent on the harmony track; needs design w/ maintainers) Band/backing model (band.json performer roster + backing config; hole-proof / single-bass / mirror-not-grade / never-invents-the-player's-line invariants) — opens as its own FEP once the harmony track settles

Design notes maintained locally (feedpak-format-extension-plan.md).