feat(showcase): add grain-sacks (#252)

Grain sacks were the next unclaimed showcase candidate. What an envelope
check cannot see on a sack is whether it has settled: an egg-bottomed
sack still touches the floor at its lowest vertex, so zmin and the
per-sack support gate both pass it. The piece sums the flat-on-floor face
area under each sack, and --round-bottom exits 19 with every patch at 0
while zmin and the supports still pass.

Also asserts each twine tie sits in its neck's waist, bites the cloth by
a banded depth, and that the sacks press into one another and carry their
belly low, each with a falsifier proven on 4.5.11, 5.1.2 and 5.2.1.

Signed-off-by: TMHSDigital <154358121+TMHSDigital@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: TMHSDigital

.cursor-plugin/plugin.json

@@ -166,6 +166,7 @@
     "showcase/hay-bale",
     "showcase/crate-stack",
     "showcase/stone-archway",
-    "showcase/rope-bridge"
+    "showcase/rope-bridge",
+    "showcase/grain-sacks"
   ]
 }

CLAUDE.md

@@ -22,7 +22,7 @@ rules/<rule-name>.mdc          - Anti-pattern rules, 9 total
 templates/<template-name>/     - Starter projects, 3 total
 snippets/<snippet-name>.py     - Standalone code patterns, 27 total
 examples/<name>/               - Runnable smoke-gated examples, 59 total (+ gallery.json)
-showcase/<name>/               - Budget-conformance props, 29 pieces (sibling of examples/; see showcase/README.md)
+showcase/<name>/               - Budget-conformance props, 30 pieces (sibling of examples/; see showcase/README.md)
 scripts/build_gallery.py       - Regenerates docs/gallery/ from examples/gallery.json + showcase/gallery.json
 scripts/site/                  - Vendored landing-page build (Jinja2)
 docs/gallery/                  - Committed generated gallery pages + hero renders

README.md

@@ -18,7 +18,7 @@
 </p>
 
 <p align="center">
-  <strong>16 skills</strong> &nbsp;&bull;&nbsp; <strong>9 rules</strong> &nbsp;&bull;&nbsp; <strong>3 templates</strong> &nbsp;&bull;&nbsp; <strong>27 snippets</strong> &nbsp;&bull;&nbsp; <strong>59 examples</strong> &nbsp;&bull;&nbsp; <strong>29 showcase pieces</strong>
+  <strong>16 skills</strong> &nbsp;&bull;&nbsp; <strong>9 rules</strong> &nbsp;&bull;&nbsp; <strong>3 templates</strong> &nbsp;&bull;&nbsp; <strong>27 snippets</strong> &nbsp;&bull;&nbsp; <strong>59 examples</strong> &nbsp;&bull;&nbsp; <strong>30 showcase pieces</strong>
 </p>
 
 <p align="center">
@@ -37,7 +37,7 @@
 
 ## Overview
 
-This repository ships **16 skills, 9 rules, 3 templates, 27 snippets, 59 examples, and 29 showcase pieces** for Blender Python development targeting Blender 5.2 LTS (current stable) with Blender 4.5 LTS fallback support. Blender 5.1 is prior stable.
+This repository ships **16 skills, 9 rules, 3 templates, 27 snippets, 59 examples, and 30 showcase pieces** for Blender Python development targeting Blender 5.2 LTS (current stable) with Blender 4.5 LTS fallback support. Blender 5.1 is prior stable.
 
 The content is consumed by AI coding agents reading these files directly from a checkout — **there is no MCP server in this repository, and none is required**. Cursor applies `rules/*.mdc` automatically wherever their scope globs match and takes skills by name in chat; Claude Code reads `skills/` and `rules/` from the project workspace, or from this repo kept as a referenced checkout. Any agent that can read files in a workspace can use it the same way. There is no build step for the content — edit the Markdown and Python files directly.
 
@@ -106,7 +106,7 @@ per-script exit-code model, are in
 Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](showcase/README.md).
 
 <details>
-<summary><strong>29 showcase pieces</strong> — click to expand the preview grid</summary>
+<summary><strong>30 showcase pieces</strong> — click to expand the preview grid</summary>
 
 <p align="center">
   <a href="showcase/shipping-crate/"><img src="showcase/shipping-crate/preview.webp" width="24%" alt="Shipping crate: a wooden slat crate with iron corner brackets on a dark studio floor, warm wedge on the back wall" /></a>
@@ -138,6 +138,7 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show
   <a href="showcase/crate-stack/"><img src="showcase/crate-stack/preview.webp" width="24%" alt="Crate stack: three slatted shipping crates stacked and yawed, each with iron corner straps and runners, on a dark studio floor" /></a>
   <a href="showcase/stone-archway/"><img src="showcase/stone-archway/preview.webp" width="24%" alt="Stone archway: a semicircular masonry arch with coursed piers, projecting imposts, nine voussoirs and a proud keystone, on a dark studio floor" /></a>
   <a href="showcase/rope-bridge/"><img src="showcase/rope-bridge/preview.webp" width="24%" alt="Rope bridge: a sagging plank deck on foot ropes between two pairs of log posts, with lashed hemp hand ropes, suspenders, and ropes staked to the ground, on a dark studio floor" /></a>
+  <a href="showcase/grain-sacks/"><img src="showcase/grain-sacks/preview.webp" width="24%" alt="Grain sacks: three burlap sacks gathered and tied with twine, two standing and one lying slumped in front, one blue-striped and one red-striped, on a dark studio floor" /></a>
 </p>
 
 [`shipping-crate`](showcase/shipping-crate/) — procedural crate through UVs, bake, LOD, collider, and Unity glTF, asserting recomputed budgets. Falsifier `--skip-decimate` exits 9.
@@ -194,6 +195,8 @@ Budget-conformance props. Not examples. Conventions: [`showcase/README.md`](show
 
 [`rope-bridge`](showcase/rope-bridge/) — procedural rope footbridge whose plank deck is fitted to a parabola recomputed from the plank tops, with lashed hand ropes and staked foot ropes, through the same pipeline. Falsifiers `--vee-deck` exits 19, `--float-suspenders` exits 18.
 
+[`grain-sacks`](showcase/grain-sacks/) — procedural pile of burlap grain sacks settled onto flat bases and tied with twine, through the same pipeline. Falsifiers `--round-bottom` exits 19, `--slip-tie` exits 17.
+
 </details>
 
 ## Examples

ROADMAP.md

@@ -134,7 +134,7 @@ Not committed; target list for the next content version. (v0.3.0 shipped the smo
 - ~~Stack of shipping crates as a game-prop showcase piece~~ **SHIPPED** as `showcase/crate-stack/` — one generator called three times with a per-instance seed driving yaw and plank widths, crates seated on the lid below; `--same-seed` exits 20 on the per-instance variation budget, `--float-stack` exits 18 on the seat
 - ~~Keystone archway with voussoirs as a game-prop showcase piece~~ **SHIPPED** as `showcase/stone-archway/` — coursed piers, projecting imposts, nine voussoirs, proud keystone; the intrados circle fit is recomputed from vertex positions and `--off-circle` exits 19 on it while leaving every other budget passing
 - ~~Rope bridge (planks, rope rails, sag between anchors) as a game-prop showcase piece~~ **SHIPPED** as `showcase/rope-bridge/` — log posts, through-tenoned sills, twenty planks seated on laid foot ropes, lashed hand ropes, suspenders, staked tie-offs; a least-squares parabola is fitted to the plank tops and `--vee-deck` exits 19 on it with the sag still in band
-- Grain sacks (cloth sacks, some slumped, tied necks) as a game-prop showcase piece
+- ~~Grain sacks (cloth sacks, some slumped, tied necks) as a game-prop showcase piece~~ **SHIPPED** as `showcase/grain-sacks/` — three settled, pleated burlap sacks, one lying, twine ties seated in the neck waist, sacks pressed into one another; flat contact patch summed from the mesh, `--round-bottom` exits 19 on it while zmin still passes
 - Brazier (iron bowl on legs, coals, ash) as a game-prop showcase piece
 - Apothecary shelf (shelf unit, bottles and jars of varied form) as a game-prop showcase piece
 - Wooden yoke (oxbow, iron rings) as a game-prop showcase piece