[vaprdev]

Summary

Clouds were either puffy or streaky, shaded the same everywhere. They now come in kinds, are lit from the sun or moon, and can cast shadows on the ground.

-makeClouds(count, puffy, y0, y1)
+makeClouds(count, kind, y0, y1)      cumulus | towering | cirrus | wisp | stratus | ash
-paintClouds(..., alpha, puffy)
+paintClouds(..., alpha, orb)         lit side faces the orb, backlit glowing edges near it
+makeShadows() / paintShadows()       soft cloud shadows drifting over the ground
+paintHaze()                          static haze band

Each wallpaper picks its own kinds (towering cumulus on the horizon, ash over the volcano, and so on), thin clouds are thickened enough to read in the terminal, and each cloud's shape is built once per screen size so drawing them each frame stays cheap.

Evidence

Before (main) on the left, after on the right.

Day

Verification: bun run typecheck passes; CI's check job runs dev/check.ts on this branch.

Merge Danger

Door: two-way

Blast Radius: API

makeClouds and paintClouds change signature (a kind instead of puffy, an orb instead of puffy); third-party wallpapers calling them need updating. The template and CONTRIBUTING are updated.

Merged together with the other visual improvements in #1; this PR's CI screenshot check fails by design because screenshots are regenerated there.