feat(editor): add --gen-dock-pack composite

Seventh themed mesh pack after camp / blacksmith / village /
temple / graveyard / garden. Harbor / dockyard scene
emitting a 7-primitive port-side layout:

  • dock — the pier itself
  • crate-stack — cargo waiting to be loaded
  • barrel — sailor stash
  • canopy — shade for the dockmaster's station
  • bench — passenger waiting area
  • signpost — port marker
  • hitching-post — for tying up small boats / mounts

Together these form a recognizable harbor / dockside
pickup-and-drop area when arranged in a zone.

Composite-pack catalogue: camp + blacksmith + village +
temple + graveyard + garden + dock = 7 themed mesh packs.

tools/editor/cli_arg_required.cpp

@@ -61,7 +61,7 @@ const char* const kArgRequired[] = {
     "--gen-mesh-hitching-rail", "--gen-mesh-pillar-row",
     "--gen-camp-pack", "--gen-blacksmith-pack", "--gen-village-pack",
     "--gen-temple-pack", "--gen-graveyard-pack",
-    "--gen-garden-pack",
+    "--gen-garden-pack", "--gen-dock-pack",
     "--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",