fix(showcase): anvil and campfire visual quality pass

[TMHSDigital]

Summary

Visual quality pass on anvil and campfire — the two remaining pieces that had never had one. Three inspection rounds on 5.2.1. 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 market-stall / watchtower (largest remaining unpassed silhouettes).

Anvil

Defects (inspection sheet, rounds 1–2)

1. Horn loft twisted into a needle/ribbon — front ortho, three-quarter, wire spikes.
2. Pritchel was a star of internal faces (rect-8 to octagon index mismatch) — clay, top, joint-horn.
3. Face was segmented boxes with black seam lines — three-quarter, clay.
4. Round-1 leftover: circular tori on a 24-gon, nubs glued on as holes, no coopered staves, huge overhanging slab.

Round 3: horn is an oval cone, hardy and pritchel are through-holes in one slab, stump/hoops/waist/foot seated. Face is still a razor-edged London bar (no iron bevel); that is remaining polish, not a budget fail.

Structural fixes

• One add_slotted_slab for the face (grid around two hole cells) instead of welded boxes.
• Horn as circular/oval rings with a shared N_SECTION parameterization — no superellipse morph.
• Hoops from host_outer_r stave chords; --round-band uses a circle.
• Foot-on-head BVH gap; --float-anvil lifts the iron 10 mm so bbox 8 still passes and 17 fires.
• Camera from measured AABB span (no deviation=).

Budgets (4.5.11 / 5.1.2 / 5.2.1)

Axis	All three
tris	2988 (was 6616)
LOD	0.5000 / 0.2195
mats	1040 wood / 822 metal
AABB	0.621 × 0.414 × 0.489 m, zmin 0
hygiene	all 0
staves	16, stave_z 0
hoop bite	0.00300
seat	0.00300
collider	134
export	244052 / 244052 / 244036

Flag	Exit	Budget
default	0	—
--skip-decimate	9	LOD1 ratio
--stray-vert	15	loose verts
--lift-z	16	zmin
--short-staves	16	named staves
--float-anvil	17	foot-on-head
--round-band	18	hoop bite

Inspection rounds: 3. Framing on 5.2.1: fill y=0.800, margins ok. No deviation=.

Campfire

Defects (inspection sheet, rounds 1–2)

1. Upper course floated with a mortar gap — front ortho, joint-running-bond.
2. Teepee caps ended ~7 mm apart at one point — joint-teepee-apex.
3. Angular daylight between running-bond wedges — elevation orthos.
4. Round-1 leftover: identical boxes, empty pit, floor logs floating.

Round 3: courses share Z, teepee crosses at the apex, ash fills the pit, 14 wedges grounded. Stones still read as bricks more than cobbles; silhouette is a campfire.

Structural fixes

• Courses stacked on row * STONE_H (shared plane). --gap-courses inserts COURSE_GAP.
• Apex ring (STICK_R * 0.55) / sin(π/N) plus overshoot past the kiss point. --float-logs inflates the ring.
• GAP_ANG 0.004 from the span function, not per-stone nudges.
• Three-Z barrelled wedges; remove_doubles after bevel.
• Camera from measured AABB span (no deviation=).

Budgets (4.5.11 / 5.1.2 / 5.2.1)

Axis	All three
tris	2200 (was 3616)
LOD	0.5000 / 0.2200
mats	1304 stone / 216 wood / 48 ash
AABB	0.807 × 0.808 × 0.404 m, zmin 0
hygiene	all 0
stones	14, stone_z 0
kiss	0.00001
course seat	0
collider	198
export	206244 / 206244 / 206236

Flag	Exit	Budget
default	0	—
--skip-decimate	9	LOD1 ratio
--stray-vert	15	loose verts
--lift-z	16	zmin
--short-stones	16	named bottom stones
--float-logs	17	teepee kiss
--gap-courses	18	course seat

Inspection rounds: 3. Framing on 5.2.1: fill y=0.733, bottom margin 0.033. No deviation=.

Evidence

• Live run: default + all named falsifiers on .scratch/blender-4.5.11-windows-x64, blender-5.1.2-windows-x64, blender-5.2.1-windows-x64 (binaries self-report those versions). Hero stills Cycles 5.2.1. Generated HTML alts/witnesses read back after python scripts/build_gallery.py.
• Inspection only: six orthos, two three-quarters, clay, wire, joint close-ups, ground contact in .scratch/qpass/ (untracked).
• Did not touch examples, skills, snippets, rules, templates, gallery_framing.py, LICENSE, VERSION, CHANGELOG, release/smoke/pages workflows.

Test plan

• Validate + blender-smoke 5.2 and 4.5 green
• needs-5.1 labeled; 5.1 smoke green
• Socket Security not failing
• Squash-merge, tag, Pages, gallery 200

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