feat(keys_highway_3d): add note-colour palettes and selectable camera angles (#794)

* feat(keys_highway_3d): add note-colour palettes and selectable camera angles

Give the 3D keys highway player-facing view options and a tuned default
look, so the piano highway is readable out of the box and customisable
from the settings panel without touching code.

Note colours (settings -> Note colours, `keys3d_bg_palette`):
- Octaves (new default): each octave its own hue climbing the rainbow,
  darker sharps, so pitch height reads at a glance on any note range.
- Rainbow: the original per-pitch table (colours unchanged).
- Vivid / Pastel: per-pitch variants.
- Emerald / Ice: single-hue two-tone (uniform naturals, darker sharps).
The pick drives the notes, key glow, lane guides and hit flames, live.

Camera (settings -> Camera angle, `keys3d_bg_camera`):
- Classic (the original low rig) / Elevated / Overhead (new default).
- Height, distance and tilt fine-tune sliders nudge the base vantage the
  auto-pan/zoom follow-motion orbits; presets apply live.

The new defaults are opinionated for plug-and-play (octaves palette,
overhead camera, tilt -0.6); anyone who prefers the original look can
pick Rainbow + Classic. Settings changes are re-read on init() so they
apply on return from the settings screen, not only after a relaunch.

Scoring, hit-timing and MIDI handling are untouched -- these are purely
visual. Numeric FX keys clamp to declared ranges (FX_RANGES); the pure
colour/camera helpers are covered by unit tests (node --test).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: LegionaryLeader <legionaryleader@gmail.com>

* fix(keys_highway_3d): make Classic camera reproduce the original rig + drop per-frame camera alloc

Review follow-ups on the palettes/camera feature:

- "Classic" preset now reproduces the historical rig exactly. The tuned
  plug-and-play downward aim (camTilt -0.6 x CAM_TILT_UNITS = -33) is baked
  into CAM_PRESETS.overhead.lookY, and camTilt now defaults to 0 (neutral).
  The default overhead look is byte-identical (effective lookY still -33),
  but "pick Classic for the original look" is now actually true instead of
  leaving a -33 down-tilt applied. settings.html tilt slider defaults to 0.

- _rig() writes into a hoisted reusable object instead of allocating a fresh
  {y,z,lookY,lookZ} literal every frame, honoring the module's documented
  "no per-frame allocations in draw()" discipline. Callers read it
  synchronously and never retain it, so one shared instance is safe.

Tests updated for the neutral camTilt default; adds an invariant test that
the default overhead framing is unchanged and Classic + neutral tilt == the
historical LOOK_Y. Full JS suite green (1069 pass).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Signed-off-by: LegionaryLeader <legionaryleader@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

plugins/keys_highway_3d/README.md

@@ -3,10 +3,11 @@
 RS+-style falling-note 3D piano highway for [Slopsmith](https://github.com/got-feedback/feedback), fed by the **Sloppak Notation Format** (sloppak-spec §5.3) — part of the piano/keys first-class epic (slopsmith#828, plugin workstream slopsmith#824).
 
 - Consumes the `notation_info` / `notation_measures` highway-WS stream over a private per-instance socket and flattens measure → staff → voice → beat → note into `{midi, t, durSec, hand}` (durations derived from written `dur`/`dot`/`tu` at the running tempo; ties extend; overlap-clamped).
-- 3D perspective highway to a vanishing point with a real white/black-key keyboard; per-key **pitch-class colours** (Synthesia convention — C red, D yellow, E blue, …) with hand (rh/lh) as a secondary brightness cue.
+- 3D perspective highway to a vanishing point with a real white/black-key keyboard; per-key **pitch-class colours** (Synthesia convention — C red, D yellow, E blue, …) with hand (rh/lh) as a secondary brightness cue. Selectable **note-colour palettes** (settings → Note colours, `keys3d_bg_palette`, default the per-octave scheme): a per-octave rainbow (each octave its own hue, darker sharps), the original per-pitch "Rainbow" table, vivid/pastel per-pitch variants, and single-hue two-tone palettes (uniform naturals, darker sharps) for players who want "black key coming" to read at a glance; notes, key glow, lane guides and hit flames all follow the pick live.
 - Full RS+ visual treatment: key **letter glyphs** printed on the active-range key tops (cached CanvasTextures), **bevelled gem-style note blocks** (ExtrudeGeometry, geometry/material caches keyed by size and pitch-class×hand), **floating bar numbers** scrolling with the notes, **active-range lane dimming** so the playable span pops, and a **glowing pulsing hit-line** (layered additive gradient planes — no postprocessing).
 - Performance discipline: no per-frame allocations or DOM queries in `draw()`. Chart-scoped resources — note geometries/materials, bar-number and glow textures — are cached and disposed on chart teardown; the key-letter glyph `CanvasTexture`s live in a shared module-level cache that survives teardown and is reused across instances.
 - Auto-selected for arrangements with notation via `matchesArrangement(songInfo.has_notation)`; capability-native `visualization` provider declaration.
+- **Camera settings**: camera-rig presets (`keys3d_bg_camera` — classic low rig / elevated / overhead; default overhead, applied live, adaptive pan-zoom preserved) with base-rig fine-tune sliders for height, distance and tilt (`keys3d_bg_camHeight` / `camDist` / `camTilt`) that nudge the vantage point the follow-motion orbits. Numeric FX keys clamp to per-key declared ranges (`FX_RANGES`, default 0–1).
 - **Web MIDI input scoring**: module-level MIDI singleton (one access per tab, focused-instance routing) with device auto-connect by saved id+name, loopback blocklist, channel filter, transpose and CC64 sustain (`keys3d_` localStorage prefix; `window.keysH3d*` settings API). Hit detection matches played MIDI against the flattened chart notes within ±0.10 s with per-note dedupe and a missed-note sweep (only while a device is connected — never retroactive across a mid-song connect).
 - **Live hit feedback on the MIDI path** (not the chart): key depress (~4° back-edge pivot, ~120 ms spring; the key letter rides along), wrong-note red key flash, and a vertical flame flare on hits (pooled additive sprites, white-hot base fading into the pitch-class colour, ~400 ms).
 - **End-of-run stats**: POSTs `/api/stats` `{filename, arrangement, score, accuracy}` exactly once per run with the same formula as the guitar notedetect path (`accuracy = hits / max(1, hits+misses)`, `score = round(hits·100·accuracy)`), then notifies the progression core when present.