Wildlife and nature: animals, beehives, bushes, flowers, rocks, logs

New stdlib module wildlife.rhai:
- Animals (new palette category): Deer (stag with antlers, does, fawns),
  Wild boar, Fox, Elephant (bull with tusks, cow, calf), Rabbits. Low-poly
  solids from faces (loft, tube), parts drawn back to front by depth, faces
  edged in their own shade (class beast). Herds scatter round a spot, each
  animal its own sprite facing about the object's rotation. Grazing
  animals switch between two head poses (iso-pose2 groups), elephants curl
  their trunks, rabbits hop.
- Birds and Butterflies as flocks: swim() takes a shape (bird, fly, bee);
  wings flap out of step. Fish output unchanged.
- Beehives on stands with supers, lids, entrances and bees flying round;
  Bush (round, flowering, berries); Flowers (bed in rows or meadow); Rocks;
  Log or stump. g-meadow and g-soil ground materials.
- polyline() takes 3D points as documented (antlers).

Theme colours for dark and light, viewer CSS for poses, flapping, hopping.
examples/country: elephants in a paddock with a cut corner, deer at a
forest edge, boar, fox, rabbits, an apiary by a meadow, a pond, a lane,
fence and hedgerow at angles; Country demo in the web Studio and deploy.
MCP guidance, README, SCRIPTING, ROADMAP.

Tests: Rust 78, Studio 122; existing examples draw the same (only the
embedded theme CSS grew).

docs/SCRIPTING.md

@@ -88,11 +88,11 @@ shaded automatically by face direction.
 | `flat(poly or polys, z, cls[, id])` | flat polygon(s); later ones cut holes |
 | `open(a, b, [[u0, u1, z0, z1], …], cls[, id])` | windows / doors on the face a→b (outward normal on the right) |
 | `lines(segs, z, cls)`, `disc(cx, cy, z, r, cls[, id])` | markings |
-| `polyline(lines, z, cls)` | open lines through plan points at height z (or 3D points): a dashed line stays one dash run round a curve |
+| `polyline(lines, z, cls)` | open lines through plan points at height z, or 3D points `[x, y, z]` (antlers): a dashed line stays one dash run round a curve |
 | `circle(x, y, z, r_px, cls[, dx, dy])`, `stem(x, y, z0, z1, w_px, cls)` | screen-space details (crowns, poles) |
 | `person(x, y, z[, cls])`, `sit(x, y, z, cls)`, `head(x, y, z, r)`, `led(x, y, z[, cls])` | figures |
 | `puffs(x, y, z[, kind[, n, dur]])`, `fan(x, y, z, r)` | animated steam / smoke / fans |
-| `swim(x, y, z, [#{ rx, ry, dur, delay, cw, len, cls }, ...])` | fish going round ellipses (radii rx, ry along the object's axes) about (x, y) on the plane at z, one round per `dur` s, clockwise when `cw`; `cls` koi / koiw / koig (the pond) |
+| `swim(x, y, z, [#{ rx, ry, dur, delay, cw, len, cls[, shape] }, ...])` | fish going round ellipses (radii rx, ry along the object's axes) about (x, y) on the plane at z, one round per `dur` s, clockwise when `cw`; `cls` koi / koiw / koig (the pond); `shape` "bird" (wings `len` across, flapping), "fly" (a butterfly) or "bee" makes it a flock |
 | `seq([[x, y, \|q\| …], …])` | items drawn back to front by their anchor |
 | `group(cls[, css], \|q\| …)`, `begin(cls[, css])` … `end()` | `<g>` around parts (animation) |
 | `ext(x, y, z)`, `ext_box(…)` | widen the sort box |
@@ -145,6 +145,27 @@ orders them, the one on the viewer's side going later. A long diagonal wall
 therefore sorts right against everything on either side of it, and mitred
 pieces against each other.
 
+## Animals
+
+`wildlife.rhai` draws animals as low-poly solids from faces. `s.loft(spine,
+rs, n, [side, cap0, cap1])` sweeps an n-sided ring (radius r, or `[across,
+up]`) along 3D points, keeping its turn round bends; `s.tube(a, b, ra, rb, n,
+mat)` is a loft of two rings. `face` shades each face by its direction and
+leaves out the ones turned away, so a solid needs no sorting of its own
+faces; separate parts (legs, body, neck, head, antlers) are drawn back to
+front by `draw_parts`, which sorts them by the depth of their anchors in the
+view (`depth(x, y) + z`). The class `beast` edges each face in its own shade
+instead of the dark outline, so a body reads as one surface.
+
+`animal_parts(kind, sub)` returns `#{ body, up, down }` for an animal facing
++x: the parts that stay and two head poses. With grazing on, the poses sit in
+two groups `iso-a iso-pose2 iso-pose0` and `iso-a iso-pose2` that take turns
+(the CSS shows the first unanimated); each animal starts at its own point of
+the cycle. `herd(o, kind, mix, graze)` scatters `n` animals in a sunflower
+spread within `r` of the object, each facing its rotation give or take 70°,
+each its own sprite. Flocks of birds, butterflies and bees use `swim` with a
+`shape`.
+
 ## Production lines
 
 `producer`, `conveyor` and `robot_arm` (stdlib/industry.rhai) work together