fix(showcase): remodel fern-mossy-rock with a cleaved gritstone boulder and feathered, lobed moss

The boulder read as a smooth grey lump and the moss as a carpet with a hard
vertical front edge; the piece sat wide and low in its panel. Rebuilt:

- boulder: ellipsoid 0.74 x 0.60 x 0.80 (was 0.56 high), cut by twelve deep
  planes (0.50-0.58 of the support, was 0.64-0.72) through 16-20 mm bevels
  (were 35-110 mm), so broad flat fracture faces meet at crisp, weathered
  arrises; two stepped ledges (region beyond both of two planes removed);
  flat faces keep a tenth of the waves (was 40%); lattice 28 -> 36 (high
  40 -> 52). Crack plane moved to the stone's middle so the V reads down its
  front, with the crack fern growing out of it in view of the hero camera
- stone shader: warm buff to grey mottling, weathered grey rind, quartz grit,
  pitting in the bump, rain streaks on steep faces only, algae, sage and
  orange lichen and dark crust spots, a green stain round every cushion
  (MossD point attribute, distance to nearest moss) and a dark damp band at
  the foot (SoilH, height over the bank)
- moss: lobed outline (broad lobes, deep inlets); height full in the middle,
  feathering to nothing over the outer 42% of the radius, up to 1.8x deeper
  in the stone's hollows; two bare patches dip under the stone; the rim runs
  over the crack's lip; nine satellite tufts; each shell tucked to its own
  depth (two rims on one flat fracture face were coplanar)
- composition: crown moved to the boulder's front-right foot, soil disc
  0.95 x 0.78 (was 1.12 x 1.03), camera 4.0 -> 3.55 m; litter 48, pebbles
  14, sorrel 7 clumps, placed sorrel first so the tighter disc holds them

Budget changes:
- Base tris 76800-77600 -> 86300-87200 (86740); face floors re-fit (16224
  stone, 4548 moss, 1728 litter, 2150 sorrel measured)
- Outer AABB -> (2.2872, 1.9008, 1.1111) m; the crack fern is the top, the
  soil disc the left and back, frond tips the right and front
- Moss seat band 0.006-0.080 -> 0.001-0.055 (0.0016-0.0463); bare-patch
  vertices are tagged Ring -2 and measured inside the stone with the rim
- New exit 27, cleaved: share of the stone's turning (dihedral x edge
  length, >20 mm over the soil, crack excluded) in arrises sharper than 20
  deg >= 0.42 (0.4856). A count of flat 0.03 m2 regions did not separate
  the recipes (the old lump had as many); where the turning happens did
- New exit 28, moss rim: each cushion's last ring before its tucked rim
  <= 0.010 m over the stone (0.0069)

Falsifiers (flag -> measured -> exit), 5.2.1 and 4.5.11 identical; tris
86740 and AABB unchanged in all:
  --skip-decimate     LOD1 1.0000                                 9
  --stray-vert        loose_v 1                                  15
  --lift-z            zmin 0.05000                               16
  --smooth-rock       crisp share 0.2892 (new; shipped recipe,
                      ellipsoid x0.90, own flat foot)            27
  --float-fronds      stalk base -0.0503 m                       17
  --lift-crown        rootstock worst sector -0.0180, 1/8        17
  --float-moss        top 0.0858, rim -0.0380 m                  18
  --slab-moss         rim ring 0.0189 m (new; shipped profile)   28
  --perch-rock        worst sector -0.0321 m, 7/8                20
  --sunny-moss        facing 0.5986                              21
  --perch-crack-fern  not in cleft, walls 0.1576 m               22
  --flat-taper        tip 0.996                                  23
  --opposite-pinnae   gaps 0.0013-0.9987                         23
  --open-crozier      0.932 turns, ratio 1.128                   24
  --float-cover       -0.046 m, 164 shells loose                 25
tests/check_falsifier_targets.py --run --only fern-mossy-rock passes.

Evidence (live runs, local):
- .scratch/5.2/blender-5.2.1-windows-x64/blender.exe (Blender 5.2.1 LTS):
  two default runs identical; hygiene 0 incl. 0 coplanar cross-shell pairs,
  0 pinnae unturned; collider 130; export 10731436 B.
- .scratch/blender-4.5.11-windows-x64 (4.5.11 LTS): all 17 runs same codes
  and values; glTF +12 B.
- .scratch/blender-5.1.2-windows-x64 (5.1.2): default exit 0, same values.
- Framing: fill x 0.822, y 0.878; margins l .131 r .047 b .044 t .078.
- Contact sheet: luma 0.2387 (band 0.2369-0.2428), stage 0.2428 (<= 0.2517),
  warmth +0.0949 (spread -0.144..+0.105), sat 0.2371. Thumbnail: split
  mossy boulder with a fern in its crack beside the fern crown.
- Asset sheet: before, a grey lump under a moss slab behind a fern; now a
  split, blocky boulder with lobed moss and the crack fern. Not the
  least-designed object (the hydrant is plainer). Weak points: bare moss
  patches read a little like cut holes up close; the soil rim is a thick
  cake edge; the rock stays in shade in the hero.
- build_gallery, check_site_links (122 pages, 0 failures), check_engine_id,
  check_exit_code_readme, check_gallery_images, check_import_export_rules,
  check_falsifier_targets pass.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: TMHSDigital

README.md

@@ -174,7 +174,7 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show
   <a href="showcase/go-kart/"><img src="showcase/go-kart/preview.webp" width="24%" alt="Go-kart: yellow go-kart on a patch of track asphalt before a red and white kerb: bent red tube chassis, black seat, finned engine with chain to the rear axle, slick tyres on silver rims." /></a>
   <a href="showcase/broadleaf-oak/"><img src="showcase/broadleaf-oak/preview.webp" width="24%" alt="Broadleaf oak: a mature oak with a massive buttressed trunk and crooked limbs reaching out under a broad dome of lumpy dark-green leaf cushions, on a grassy mound with roots, tufts and fallen leaves" /></a>
   <a href="showcase/farm-tractor/"><img src="showcase/farm-tractor/preview.webp" width="24%" alt="Farm tractor: green farm tractor in muddy ruts beside a puddle: long bonnet, barred grille, rusty exhaust stack, big lugged rear tyres on cream rims with weights, small ribbed fronts." /></a>
-  <a href="showcase/fern-mossy-rock/"><img src="showcase/fern-mossy-rock/preview.webp" width="24%" alt="Fern and mossy rock: a male fern's arching crown of finely cut fronds, with curled fiddleheads, in front of a cleft boulder cushioned in moss on a soil bank with fallen beech leaves, pebbles and wood sorrel" /></a>
+  <a href="showcase/fern-mossy-rock/"><img src="showcase/fern-mossy-rock/preview.webp" width="24%" alt="Fern and mossy rock: a male fern's arching crown of cut fronds and fiddleheads beside a split gritstone boulder with flat broken faces, lobed moss cushions and a small fern in its crack, on a soil bank with beech litter" /></a>
   <a href="showcase/sea-stack-arch/"><img src="showcase/sea-stack-arch/preview.webp" width="24%" alt="Sea stack and arch: a layered sandstone sea arch on a wave-cut rock platform, a sea stack beside it on its own island, foam at the waterline, fallen blocks, and grass and pink sea thrift on the tops" /></a>
 </p>
 
@@ -304,7 +304,7 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show
 
 [`farm-tractor`](showcase/farm-tractor/) — the ninth `vehicles` piece: procedural mid-century utility tractor standing in the ruts of a muddy farmyard with a puddle between its wheels (a cast-iron backbone of engine, bell housing, gearbox and rear axle housing with trumpets; a front axle oscillating on a pivot pin through the front support's lugs and two bushings, kingpins, spindles and a tie rod; 1.240 m rear tyres with 44 chevron bars rooted in the carcass and handed for forward travel, on dished rims with welded clamp lugs and cast-iron half-moon weights; ribbed front tyres; a grille shell with radiator and headlamps, a louvred bonnet, fuel tank and dash; a vertical exhaust stack with a hinged rain cap and an oil-bath pre-cleaner bowl; a raked steering column, a pan seat on a leaf spring, pedals and footplates; mudguards with a tail lamp and a work lamp; a three-point linkage with lift arms, lift rods, lower links, a stowed top link and the drawbar, and a PTO stub under its shield; paint chipped to primer at its edges, rust-streaked, sun-faded and mud-splashed). Asserts 122272 tris, twelve materials with face floors, zero coplanar cross-shell pairs, every tyre sunk 18–45 mm into the mud, hubs and the pivot pin coaxial, 14 link eyes on their pins, beads seated, 88 bars rooted and evenly pitched with their apex leading, body and wheels mirrored, wheelbase, tracks and rear-tyre diameter at their stated size, the mass centre inside the support triangle of the rear contacts and the front pivot by a quarter of the track, and one connected assembly; `--float-tyre` exits 16, `--cock-hub`, `--cant-pin` and `--unpin-link` 17, `--sink-tyre` and `--float-lugs` 18, `--skew-wheel`, `--wide-track`, `--tall-lugs` and `--odd-fender` 19, `--bunch-lugs` 20, `--reverse-lugs` 21, `--offset-pivot` 22, `--loose-lamp` 23, while the envelope holds.
 
-[`fern-mossy-rock`](showcase/fern-mossy-rock/) — the ninth `nature` piece: procedural shaded woodland corner on a sloping soil bank (a gritstone boulder cleaved into broken, weathered faces and split by a deep crack, sunk into the bank all round, a thick moss cushion over its crown draped down its shaded front as a conforming shell with a lumpy rim tucked into the stone, a male fern's shuttlecock crown of eleven bipinnate fronds whose 434 alternate pinnae are cut into pinnules and taper to the tip, three fiddleheads unrolling as logarithmic spirals from a scaly rootstock bedded in the soil, a smaller fern growing out of the crack, and beech litter, pebbles, a twig and wood sorrel at the foot), whose rooted fronds and rootstock, moss thickness over the stone, boulder sealed in the bank, moss facing up or into the shade, crack fern wedged in the cleft, pinna alternation and taper, true spirals and ground cover are recomputed from the mesh, through the same pipeline. `--float-fronds` and `--lift-crown` exit 17 on every frond rooted in its crown and the crown sealed in the soil, `--float-moss` 18 on the moss cushion's thickness band on the stone, `--perch-rock` 20 on the boulder sealed all round, `--sunny-moss` 21 on moss facing up or into the shade, `--perch-crack-fern` 22 on the crack fern rooted in the cleft, `--flat-taper` and `--opposite-pinnae` 23 on pinnae alternating and tapering along the rachis, `--open-crozier` 24 on every fiddlehead a real spiral, `--float-cover` 25 on the ground cover joined to the soil, while the envelope holds.
+[`fern-mossy-rock`](showcase/fern-mossy-rock/) — the ninth `nature` piece: procedural shaded woodland corner on a sloping soil bank (a gritstone boulder cut by deep cleavage planes into broad flat fracture faces meeting at crisp, weathered arrises, with stepped ledges, pitting, lichen, a moss stain and a damp band at its foot, split down its front by a deep crack and sunk into the bank all round; lobed moss cushions and satellite tufts laid on it as conforming shells, deepest in its hollows, feathering to nothing at the rim, tucked over the crack's lip, with bare patches where the stone shows through; a male fern's shuttlecock crown of eleven bipinnate fronds whose 434 alternate pinnae are cut into pinnules and taper to the tip, three fiddleheads unrolling as logarithmic spirals from a scaly rootstock bedded in the soil, a smaller fern growing out of the crack, and beech litter, pebbles, a twig and wood sorrel at the foot), whose cleaved stone, rooted fronds and rootstock, moss thickness and feathered rim, boulder sealed in the bank, moss facing up or into the shade, crack fern wedged in the cleft, pinna alternation and taper, true spirals and ground cover are recomputed from the mesh, through the same pipeline. `--smooth-rock` exits 27 on the stone's turning concentrated in crisp arrises, `--float-fronds` and `--lift-crown` 17 on every frond rooted in its crown and the crown sealed in the soil, `--float-moss` 18 on the moss cushion's thickness band on the stone, `--slab-moss` 28 on the cushion feathering out at its rim, `--perch-rock` 20 on the boulder sealed all round, `--sunny-moss` 21 on moss facing up or into the shade, `--perch-crack-fern` 22 on the crack fern rooted in the cleft, `--flat-taper` and `--opposite-pinnae` 23 on pinnae alternating and tapering along the rachis, `--open-crozier` 24 on every fiddlehead a real spiral, `--float-cover` 25 on the ground cover joined to the soil, while the envelope holds.
 
 [`sea-stack-arch`](showcase/sea-stack-arch/) — the tenth `nature` piece: procedural coastal diorama tile (a fragment of a horizontally bedded sandstone headland on a wave-cut rock platform: sixteen hard and soft beds at one set of heights in every column, the soft beds undercut so the hard beds project as ledges, vertical joint faces shared by both legs and the lintel, blocks set back and fallen out between the joints; a natural arch of two stepped legs carrying a lintel over a channel; a sea stack of the same beds on its own island; a rippled sea at a declared level with its rim under the platform, foam at the waterline, two tide pools, fallen blocks and boulders, and turf with sea grass and sea thrift on the tops), whose beds biting each other and the lintel biting both legs, stack over its footprint, feet sealed in the platform, clear aperture, level continuous bedding, undercut soft beds, sea level and ripple, contained water, seated foam, loose rock sealed and apart, and rooted cover are recomputed from the mesh, through the same pipeline. `--gap-lintel` exits 17 on every bed biting the one it lies on, `--lean-stack` 19 on the stack's mass over its footprint, `--cut-pillar` 20 on the feet sealed all round, `--close-arch` 21 on the clear aperture, `--tilt-beds` 22 on level, continuous bedding, `--flush-beds` 23 on the undercut, `--flat-sea` 24 on the water level and ripple, `--short-sea` 25 on the water contained, `--lift-foam` 26 on the foam at the waterline, `--perch-talus` 27 and `--pile-talus` 28 on the loose rock sealed and apart, `--float-cover` 29 on the cover rooted in the tops, while the envelope holds.