Sun rays: brighter, and a hard 3 degree threshold with a 2 s fade

Owner 2026-08-03: «лучи поярче, иногда плохо видны. Убрать плавное
затухание — появляться и исчезать анимацией в 2 секунды при переходе
через 3 градуса над горизонтом».

RAY_MAX_ALPHA 0.18 -> 0.30: checked against both hard cases, a daylight
sun on white paper and a low sun over the dark glow canvas
(demo/shot_sun_bright.mjs writes the pair).

The gradual ramp-in over the first ~2 degrees is gone. rayAlpha() is now a
threshold: 0 below RAY_ELEVATION_MIN (3), rayPeakAlpha(cloud) at or above
it — cloud cover stays the only multiplier. Crossing it animates the
LAYER, never the geometry: <g class='sunlayer'> fades in/out over exactly
RAY_FADE_MS = 2 s (hp-sunfade-in / hp-sunfade-out), and the card keeps the
group mounted with .out for those two seconds so the dissolve can play at
all. prefers-reduced-motion skips it. Every other reason to drop the
wedges — editor, feature off, night, rain — stays instant.

Units: rayAlpha rewritten (ramp tests dropped), raysVisible/rayPeakAlpha/
RAY_MAX_ALPHA covered. Smoke: smoke_sun gains a threshold section (8 of
its checks fail on the previous build). docs/SUN.md + TESTING.md updated.

docs/TESTING.md

@@ -931,6 +931,15 @@ require hands on real hardware — they remain for the human pass.
 - [ ] Wedge direction follows the compass; length grows toward
       sunrise/sunset and shrinks toward noon; every wedge is clipped by its
       room polygon; night = no wedges at all
+- [ ] Brightness + the 3° threshold (2026-08-03): wedges are visibly brighter
+      (peak alpha 0.30, was 0.18) yet still readable over white paper AND the
+      dark glow canvas; there is NO gradual ramp near the horizon — below 3°
+      no rays at all, at/above 3° full strength; crossing the threshold fades
+      the whole layer in/out over exactly 2 s (CSS on `.sunlayer`, the
+      geometry never moves), and `prefers-reduced-motion` makes it instant.
+      Every other way of losing the wedges (editor, feature off, night, rain)
+      stays instant [auto: smoke_sun «the 3° threshold» + unit rayAlpha/
+      raysVisible/rayPeakAlpha; shots: demo/shot_sun_bright.mjs]
 - [ ] Weather entity (optional, global): cloudy fades the wedges, rain/snow
       removes them, a dead/unknown weather sensor changes nothing
 - [ ] Sun geometry recomputes ONLY when the sun attributes or the config