feat(editor): add --gen-mesh-tent A-frame canvas tent

53rd procedural mesh primitive. Builds a watertight A-frame
tent:
  • two sloped roof panels meeting at a ridge that runs along
    the X axis
  • two triangular gables sealing the ends
  • optional inverted-V door notch carved out of the +X gable
    (parameterized by doorH and doorW; either set to 0 disables
    the cutout for a solid gable)
  • bottom face for collision-bake watertightness

Useful set dressing for Horde encampments, troll camps,
Defias bandit hideouts, scout/quartermaster overlooks, and
generic outdoor quest hubs.

Default footprint 1.6 x 1.0 with 0.9 ridge height and a
0.5 x 0.4 door notch — all dimensions overridable on the CLI.

tools/editor/cli_arg_required.cpp

@@ -49,6 +49,7 @@ const char* const kArgRequired[] = {
     "--gen-mesh-banner", "--gen-mesh-grave", "--gen-mesh-bench",
     "--gen-mesh-shrine", "--gen-mesh-totem", "--gen-mesh-cage",
     "--gen-mesh-throne", "--gen-mesh-coffin", "--gen-mesh-bookshelf",
+    "--gen-mesh-tent",
     "--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",