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.gd

@@ -0,0 +1,16 @@
+# Probe the back tattoo PNG pixel values
+extends SceneTree
+
+func _init() -> void:
+	for p in ["C:/Users/CAN/tinqs-ltd/docs/conceptart/generated-images/tattoo-marks/mark-06-hearth-warmth_back_v3.png",
+			"C:/Users/CAN/tinqs-ltd/docs/conceptart/generated-images/tattoo-marks/mark-01-chiefs-mark_arm_v3.png"]:
+		var img := Image.load_from_file(p)
+		print(p.get_file())
+		print("  size=%dx%d format(raw)=%d mipmaps=%s" % [img.get_width(), img.get_height(), img.get_format(), img.has_mipmaps()])
+		img.convert(Image.FORMAT_RGBA8)
+		var w := img.get_width()
+		var h := img.get_height()
+		for uv in [[0.5, 0.28], [0.57, 0.64], [0.5, 0.5], [0.05, 0.05]]:
+			var c := img.get_pixel(int(uv[0] * w), int(uv[1] * h))
+			print("  u=%.2f v=%.2f -> %s" % [uv[0], uv[1], c])
+	quit()