feat(ui): Grace tab — slow rotating gradient looks (16 palettes × 14 shapes) for the 28-laser window

[pyramation]

Summary

The Grace tab already existed (ring-pair colours + Shapes / Droplets & Chases). This adds the thing Dan asked for — slowly rotating colour gradients for the 28-laser window — as a second family in the same tab, and makes the existing looks understand the new grace-28 inner ring of four.

New: Gradients. GRADIENTS (16 palettes: Dawn, Stained Glass, Ocean, Ember, Moonlight, Aurora, Rose Gold, Twilight, Forest, Candlelit, Violet Hour, Coral Reef, Sunset, Spectrum, Ice Fire, Sage) × graceGradients(g) (14 looks: Wheel, Counter, Sweep, Spiral, Petals, Rings, Tide, Pendulum, Drift, Glow, Breathe, Embers, Bloom, Still) = 224 combinations. Each look maps a fixture to a point on the gradient loop from its angle/radius and drifts it with time:

var LAP = 60;                       // seconds per full lap at 1x (header speed slider scales ctx.t)
grad(u)  -> [hue, sat]              // shortest-way hue lerp between STOPS, last stop loops to first
Wheel:   paint(i, pos(i) - t/LAP)   // gradient wrapped round the window, turning
Counter: outer turns one way, inner rings the other
Sweep:   u = r·cos(angle - a)       // a straight band rotating across the window
Drift:   outer 1×, inner 1.37×, centre 0.61× — never repeats

They compile to evalPattern sources like the existing looks (no new protocol, run server-side, previewed with MiniGridPreview). Picking a new palette while a gradient look is running re-sends it recoloured, same as ring pairs do.

Fix for grace-28: CENTRE_MAX 0.15 → 0.45, so the four inner cannons (radius 0.25) are treated as "centre" like the single centre cannon of grace-cathedral. Before, they fell into the inner-twelve bucket, which also broke slot()/ringCount() on that ring (16 fixtures instead of 12).

Tests: grace-rings.test.ts now runs on both grace-cathedral and grace-28; every palette × look is checked for in-range HSB on both layouts; Wheel lap = 60 s and moves < 12° per second; Counter rings move in opposite directions; Sweep opposite sides differ; Still is static; inner four read as centre in Core.

Not verified against physical BEYOND output.

Link to Devin session: https://app.devin.ai/sessions/c4872c2982734093bdee80d04a7d5ceb
Open in Devin Desktop: https://app.devin.ai/desktop/session/c4872c2982734093bdee80d04a7d5ceb?variant=devin
Requested by: @pyramation

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

[tenki-reviewer]

Review complete. No issues found — approved ✅.

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This PR introduces the Grace rings effect for the Wavegrid desktop UI. It adds packages/ui/src/lib/grace-rings.ts, which generates dynamic laser/JS patterns (handling fixture geometry, ring splitting, and HSB color interpolation with hue wraparound and CSS conic-gradient rendering), a new grace-tab.tsx component wiring the effect into the tab UI, and a grace-rings.test.ts suite exercising the new logic.

Files	Change
packages/ui/src/lib/grace-rings.ts	New library synthesizing ring patterns and conic-gradient palettes with HSB interpolation.
packages/ui/src/components/grace-tab.tsx	New tab component integrating the Grace rings effect into the UI.
packages/ui/__tests__/grace-rings.test.ts	Unit tests covering the new pattern and color logic.

_{Reviewed commit: 3754878}