fix(showcase): market-stall and watchtower visual quality pass

[TMHSDigital]

Summary

Visual quality pass on market-stall and watchtower — the two largest remaining pieces that had never had one. Four inspection rounds on 5.2.1 (round 3 still showed a wood-U roof and a floating ladder pad; round 4 closed both). Fixes are in the generators. Hygiene 15–19 already live in showcase/README.md; this PR does not change that file.

Picks: never-passed. Next run should take stone-well / street-lantern (largest remaining unpassed silhouettes).

Market stall

Defects (inspection sheet, rounds 1–3)

1. Post-bottom cubes sat coplanar with the post end-caps and z-fought at Z=0 — bottom ortho, ground-contact, joint-post-foot.
2. Counter-leg pads shared the same bottom plane as the legs — bottom ortho.
3. Side braces occupied the counter volume (visible interpenetration) — front ortho, joint-brace, clay.
4. Awning underside sat below the front header; the hanging valance top was counted as the seat face — joint-rafter-awning, front ortho.
5. Identical slats, no roller/hem, valance read as a floating stripe slab — three-quarter, front ortho.
6. Wrap-foot audit split four plates into eight corners (round(cx*4)/4) — audit, not a silhouette defect.

Generator fixes (structural)

• Wrap plinths (add_wrap) stand off the post by half + t/2 + 0.002; Y-plates span host+2t so corners meet without coplanar overlap. No capped foot cube.
• Counter legs go to Z=0; pads removed.
• Braces sit on the post-bay centreline, not through the counter.
• Awning centreline is FRONT_H+0.012 / BACK_H+0.012; seat measures stripe faces with zmax > FRONT_H so the valance top cannot pass as the canopy.
• Slat jitter from sin(i) increased; front roller/hem added.
• Support audit clusters wraps by quadrant (sign(cx), sign(cy)).
• Camera pulled back from span-relative 1.78/2.42 to 2.17/2.95 so Layer 1 fill sits in band after the taller valance.

Hygiene (all three binaries)

Axis	Declared	4.5.11 / 5.1.2 / 5.2.1
tris	3900–5200	4324 / 4324 / 4324
hygiene (loose/nonman/doubles/zero-area/ngon/zfight)	0	0
zmin / feet / foot_z	0 / 4 / ≤1e-3	0 / 4 / 0
brace overlap / header engage / awning seat / plumb	≤1e-6 / ≥0.4·tenon / −0.002–0.010 / ≤0.008	0 / 0.0595 / 0.00378 / 0
collider	≤80	58
LOD1 / LOD2	0.32–0.62 / 0.10–0.35	0.5000 / 0.2197

Before/after tris: 4404 → 4324.

Falsifiers (same code on 4.5.11, 5.1.2, 5.2.1)

Flag	Budget	Exit
(default)	—	0
--skip-decimate	LOD1 ratio	9
--stray-vert	loose verts	15
--lift-z	zmin	16
--short-feet	named wrap feet	16
--low-brace	brace-vs-counter	17
--float-awning	awning seat	18
--rake-posts	post plumb	19

Inspection rounds: 4. Framing on 5.2.1: fill y=0.783, margins min 0.056. No deviation=. Landing-page-worthy.

Watchtower

Defects (inspection sheet, rounds 1–3)

1. Shake courses did not cover the cone; the deck-rail wood U showed through the roof — top ortho, clay, three-quarter.
2. Girt iron and girt wood shared a midplane (z-fight) — joint, wire.
3. Kick bottom coplanar with sill bottom — ground-contact, bottom ortho.
4. X-brace inner faces occupied one plane — front ortho.
5. Collar inner verts sat on post faces (doubles); 4-plate collars overlapped at corners — clay, wire.
6. Shingle row 0 at t=0 collapsed to the peak (4 zero-area faces) — top ortho, hygiene.
7. Shoes added before zmin snap, then lifted (~3 mm) — ground-contact.
8. Ladder stiles started on a 32 mm pad, so they floated — front ortho, ground-contact.
9. PLAN_XY was the post bay (1.13 m) against an eave AABB of 1.594 m — would have fired 19 on a correct plan.

Generator fixes (structural)

• Solid 4-cone plus courses with t0=(row+0.14)/N, t1=min(0.96,(row+1)/N), offset along face normal so peak/eave verts are not doubled.
• Iron collars standoff 0.002; X-plates span POST, Y-plates span POST+2t (miter, not overlap). Collars after zmin snap (z<0.005 → 0).
• Members tenon with section = POST*0.70 so end verts are not on post faces.
• Kick sits on the sill, inset 0.020 from the post plane.
• X-braces offset k*(BRACE_T+0.008).
• Ladder stiles from Z=0 (no separate foot cubes).
• PLAN_XY = 2*EAVE_HALF. Camera pulled back 1.55/2.15 → 1.98/2.75 for the taller roof.

Hygiene (all three binaries)

Axis	Declared	4.5.11 / 5.1.2 / 5.2.1
tris	6200–8200	6408 / 6408 / 6408
hygiene	0	0
zmin / shoes / shoe_z	0 / 4 / ≤1e-3	0 / 4 / 0
rail engage / band seat / plumb	≥0.012 / ≤0.010 / ≤0.010	0.0180 / 0.00200 / 0
collider	≤180	150
LOD1 / LOD2	0.32–0.62 / 0.10–0.35	0.5000 / 0.2197 (5.2 LOD2 0.2185)

Before/after tris: 5220 → 6408 (taller eave-true roof and coursed shakes, not hidden faces). Collider ceiling 80 → 180 to match the new pyramidal silhouette (measured 150).

Falsifiers (same code on 4.5.11, 5.1.2, 5.2.1)

Flag	Budget	Exit
(default)	—	0
--skip-decimate	LOD1 ratio	9
--stray-vert	loose verts	15
--lift-z	zmin	16
--short-shoes	named shoes	16
--short-rails	rail-to-post	17
--float-band	collar seat	18
--rake-posts	post plumb	19

Inspection rounds: 4. Framing on 5.2.1: fill y=0.767, margins min 0.083. No deviation=. Landing-page-worthy.

Test plan

• Default + 7 falsifiers × 2 pieces × 4.5.11 / 5.1.2 / 5.2.1 (exit codes above)
• Framing gate on 5.2.1, no deviation=
• CI blender-smoke 4.5, 5.1 (needs-5.1 via REST), 5.2
• Post-merge: tag, Pages, gallery 200