Tattoo test bed: Quaternius v3-v6 bakes + Lena pipeline (bake, de-mirror, re-UV, viewers)

Session 2026-07-23/24 additions on top of the existing Quaternius bed:
- bake_lena.gd: 6-piece bake on QuatSkin Lena (chiefs-mark/iron-spine arms,
  voyagers/storm-bearer legs, star-eye chest, hearth-warmth back); global-axis
  wrap frame + 3cm junction blend kill the elbow split line
- demirror_lena.gd: tri-level split of mirror-shared limb UVs (arms 100%->0%,
  legs 99%->5% crotch-only residual)
- reuv_lena.gd: Quaternius-style semantic re-UV (16 islands, cylinder limbs +
  cylinder head/torso with planar caps) + texture transfer; fixes armpit/chin/
  cheek planar smears; single 4096 atlas, per-side tattoos native
- main_lena / anim_lena viewers (18 UAL clips, U light toggle) + probes + shots

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

probe_lena3.gd

@@ -0,0 +1,66 @@
+# Color signature of Lena's painted bra vs bare skin (for a fabric-skip predicate).
+extends SceneTree
+
+const GLB_PATH := "C:/Users/CAN/tinqs-ltd/ariki-game/assets/quaternius/derived-bodies/Ariki_Female_QuatSkin.glb"
+
+func _init() -> void:
+	var doc := GLTFDocument.new()
+	var state := GLTFState.new()
+	if doc.append_from_file(GLB_PATH, state) != OK:
+		quit(1)
+		return
+	var scene := doc.generate_scene(state)
+	var skel: Skeleton3D = null
+	var body: Node = null
+	var stack: Array = [scene]
+	while not stack.is_empty():
+		var n: Node = stack.pop_back()
+		if n is Skeleton3D and skel == null:
+			skel = n
+		if (n is MeshInstance3D or n.get_class() == "ImporterMeshInstance3D") \
+				and String(n.name).to_lower().contains("lena"):
+			body = n
+		for c in n.get_children():
+			stack.push_back(c)
+	var mesh = body.mesh
+	if mesh is ImporterMesh:
+		mesh = mesh.get_mesh()
+	var arrays: Array = mesh.surface_get_arrays(0)
+	var verts: PackedVector3Array = arrays[Mesh.ARRAY_VERTEX]
+	var uvs: PackedVector2Array = arrays[Mesh.ARRAY_TEX_UV]
+	var normals: PackedVector3Array = arrays[Mesh.ARRAY_NORMAL]
+	var mat: Material = mesh.surface_get_material(0)
+	var img: Image = (mat as BaseMaterial3D).albedo_texture.get_image()
+	img.clear_mipmaps()
+	img.convert(Image.FORMAT_RGBA8)
+	var tw := img.get_width()
+	var th := img.get_height()
+
+	# bands: [label, ymin, ymax] — front-facing, near body midline (|x|<0.15)
+	for band in [["bra front", 1.16, 1.32], ["belly skin", 0.98, 1.07],
+			["upper chest", 1.34, 1.40], ["hip underwear", 0.82, 0.90],
+			["thigh skin", 0.55, 0.75]]:
+		var sr := 0.0
+		var sg := 0.0
+		var sb := 0.0
+		var cnt := 0
+		var rb_min := 1.0
+		var rb_max := -1.0
+		for v in verts.size():
+			var p := verts[v]
+			if p.y < band[1] or p.y > band[2] or absf(p.x) > 0.15 or normals[v].z < 0.25:
+				continue
+			var px := clampi(int(uvs[v].x * tw), 0, tw - 1)
+			var py := clampi(int(uvs[v].y * th), 0, th - 1)
+			var c := img.get_pixel(px, py)
+			sr += c.r
+			sg += c.g
+			sb += c.b
+			var rb := (c.r - c.b) / maxf(c.r, 0.001)
+			rb_min = minf(rb_min, rb)
+			rb_max = maxf(rb_max, rb)
+			cnt += 1
+		if cnt > 0:
+			print("%s: n=%d avg RGB (%.3f, %.3f, %.3f)  (r-b)/r range %.3f..%.3f" %
+				[band[0], cnt, sr / cnt, sg / cnt, sb / cnt, rb_min, rb_max])
+	quit()