fix(examples): regenerate triangulate-tangents asset sheet against the new reference set

Adds a SELECT row for the buckler to scripts/asset_sheet.py. It matches the
Buckler lathe mesh and Buckler.Rivets only. The walnut stand and kickstand
strut are display staging, not part of the asset, so they are excluded.
The asset sheet is re-rendered with the committed tooling against the
reference set from #257 (collision-hull-proxy, socket-attach-points,
vertex-color-ao, wheelbarrow, apothecary-shelf).

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

Author: TMHSDigital

docs/gallery/asset-sheets/triangulate-tangents.webp

@@ -65,6 +65,7 @@
     "grain-sacks": (r"^SacksLow$", None),
     "rope-bridge": (r"^BridgeLow$", None),
     "wheelbarrow": (r"^BarrowLow$", None),
+    "triangulate-tangents": (r"^Buckler(\.Rivets)?$", None),
 }
 
 _REF_LINE = re.compile(r"Asset-sheet gate.*?reference set — currently (.+?) — rendered", re.S)