feat(editor): add --gen-mesh-workbench crafter table

62nd procedural mesh primitive. A blacksmith / crafter
workbench built from axis-aligned boxes (uses the new
cli_box_emitter helper plus the new cli_arg_parse helpers
for all 7 optional dimension args):

  • flat top slab spanning length × depth at topT thickness
  • 4 corner legs sized so their outer faces line up with
    the top edges (post-style, no overhang)
  • optional vise box at the +X end of the top — set
    viseSize=0 for a bare bench
  • optional raised tool tray along the +Z back edge —
    set trayH=0 to omit

Pairs naturally with --gen-mesh-anvil (existing) for
blacksmith forge scenes, and --gen-mesh-cauldron for
alchemist labs. Default 1.6×0.7×0.85 m bench reads at
realistic adult-human working height.

Watertight under weld (verified via --info-mesh-stats:
126 manifold edges, 0 boundary, 0 non-manifold).

tools/editor/cli_arg_required.cpp

@@ -52,6 +52,7 @@ const char* const kArgRequired[] = {
     "--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-bedroll",
+    "--gen-mesh-workbench",
     "--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",