feat(editor): add --gen-mesh-bedroll camp sleeping prop

61st procedural mesh primitive. Builds a bedroll prop:

  • horizontal closed cylinder along the Z axis sitting at
    y = R so it rests on the ground (radius defaults to
    0.16 m, length 1.4 m — adult-human-shaped)
  • optional pillow box at the +Z end (squashed cube,
    pillowSize controls extent)
  • per-segment N-sided cylinder uses the new addVertex
    helper; pillow uses addFlatBox

Set pillowSize=0 for a bare rolled mat. Watertight under
weld (verified via --info-mesh-stats: 90 manifold edges,
0 boundary, 0 non-manifold).

Pairs naturally with --gen-mesh-tent / --gen-mesh-firepit /
--gen-mesh-canopy for outdoor camp scenes — completes the
tent-side camping kit.

tools/editor/cli_arg_required.cpp

@@ -51,7 +51,7 @@ const char* const kArgRequired[] = {
     "--gen-mesh-throne", "--gen-mesh-coffin", "--gen-mesh-bookshelf",
     "--gen-mesh-tent", "--gen-mesh-firepit", "--gen-mesh-woodpile",
     "--gen-mesh-canopy", "--gen-mesh-haystack", "--gen-mesh-dock",
-    "--gen-mesh-pergola", "--gen-mesh-chimney",
+    "--gen-mesh-pergola", "--gen-mesh-chimney", "--gen-mesh-bedroll",
     "--gen-mesh-table", "--gen-mesh-lamppost", "--gen-mesh-bed",
     "--gen-mesh-ladder", "--gen-mesh-well", "--gen-mesh-signpost",
     "--gen-mesh-mailbox", "--gen-mesh-tombstone", "--gen-mesh-crate",