Brush tree: the operator's bar for a finished hull part

Clean unbroken topology flow, part-coherent low-distortion UVs, one-segment
bevels with face-weighted normals; her bevel test render as the reference.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/research/shippable-bar/README.md

@@ -0,0 +1,20 @@
+# What a finished hull part is (operator, 2026-10-10)
+
+The bar the brush-tree output is judged against. Operator's words:
+
+> A part is done for me when its topo flow is reasonably clean and unbroken, and I try to unwrap such
+> that parts of the same object stay together with minimal distortion. Bevels are used to sharpen edges
+> (sharp shading requires duplicating geo anyway, while a single faced bevel shades flawlessly with
+> face-weighted normals. See this test render showing a simple bevel, face weighted simple bevel, and
+> expensive perfect bevel next to each other, and a little test box showing off that and decals for that
+> Star Citizen effect)
+
+`operator-bevel-test.webp`, left to right: single-segment bevel with plain normals; the same bevel with
+face-weighted normals (the target look); a multi-segment "perfect" bevel (too expensive); a test box
+with face-weighted bevels and decals (decals are the separate panel-decals campaign).
+
+Measurable reading of the bar:
+- Topology: clean, unbroken edge flow (quad-dominant loops, few poles, no triangle fans or slivers).
+- UVs: islands follow the object's parts, kept together, with minimal stretch.
+- Edges: one-segment bevels on hard edges, shaded with face-weighted normals; no duplicated split
+  geometry for sharpness, no multi-segment bevels.