[quefreen]

Nav rail:

• Drop the collapsible Experiments group; 3D and Web (Boards stays gated off entirely, see below) list directly in the main rail instead of behind a submenu.
• Remove Board from the rail and from the route entirely: BoardStage can crash (composedPoseLayers reads values.offset before it's merged) when the scene has no active track, so it stays closed everywhere rather than half-shipped.
• Add a GitHub link to the rail, between Docs and the theme toggle.
• Rename nav labels: Mockup -> Devices, 3D -> OBJ.

Painted Shader (three3d/cartoon.ts):

• Fix a real bug: a CSS class shared with the 2D canvas's PNG- transparency checkerboard (.stage-canvas, !important) was clobbering the 3D stage's own inline background-fill style, so the checkerboard rendered as a permanent overlay regardless of the chosen Background Fill. Split it into its own .stage-transparency- checker class, applied only where a canvas draws opaque pixels over it.
• Fix real cross-contamination with Devices: background/sun state (bgFill, bgTexAmount/Scale, sunIntensity/Shadow, sunMask + transform) lived in one shared use3DStore slot read by both effects. Tuning Devices' studio backdrop silently retuned the Painted Shader's too, and opening a Mockup project overwrote it outright. Scoped per effect id (environments: Record<effectId, Environment>), same pattern already used for the model transform, with its own dark moody default for the Painted Shader vs. Devices' bright studio one, and a migration path for blobs persisted before the split.
• Fix another real bug: cartoon.ts called apply3DAnimation() - Devices' 16-preset camera/lighting choreography - reading use3DStore's mockupAnimation/mockupSpeed. Even at the 'static' default this silently overrode the camera's fov every frame: (42 instead of 45), and any non-static preset left over from a Devices session hijacked the orbit camera entirely. Removed; the Painted Shader now only ever drives its own free-orbit camera.
• Retune the default look: Key Light 2.6 -> 0.3, Ambient 0.5 -> 0.1, and drop the ACESFilmicToneMapping added mid-session to tame blown highlights - its filmic curve lifts shadows/midtones too, reading as a wash over the whole scene; the actual fix was the cross-contaminated background above. NoToneMapping (the default) is what the scene was designed against.
• Center the model by default: DEF_OFFSET fought fitAndCenter's own bbox-centering with a stale (-0.8, 0.7) nudge. Zeroed, so an untouched model (and "Center model") land on the canvas's true centre in any viewport.
• Drop the timeline for this section: nothing advances its clock on its own (it's a still, not a played clip), so Timeline gained a showScrubber prop to hide the play/scrubber/duration/layers row for it. Export itself is also hidden for now (no export defined for this scene yet), and the now-empty footer collapses via a new .app-3d layout class instead of leaving a dead bar on screen.