feat: A-frame tent + portal walk-through field + texture polish

- camping: replace cube tent with A-frame slope panels (tent_panel_l/r) +
  cardinal_direction permutations; vote-skip sleep that mixes
  player.isSleeping bed sleepers with tent occupants and respects the
  playersSleepingPercentage gamerule; new weathered-canvas texture.
- lobby: walk-through silverlabs:portal_field block (no collision,
  translucent swirl, cross-plane geo) auto-placed above each portal frame;
  invisible silverlabs:portal_label entity floats above each portal with
  the destination world name; transfer detection now scans down through
  the field to find the destination frame.
- postal: regenerate post_office and mailbox block textures so they fill
  the full block face (brick + POST plaque, full red panel with slot/latch
  /flag/rivets) instead of small sprites floating on transparent.
- dynamite + tow-boat: ship the addons (volumes wired into all four
  worlds; enabled_packs registers them into Mya's world).
- art: build-textures.py extended; build-art-catalog.py added to project.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lobby-addon/lobby_transfer_BP/entities/portal_label.json

@@ -0,0 +1,26 @@
+{
+  "format_version": "1.21.0",
+  "minecraft:entity": {
+    "description": {
+      "identifier": "silverlabs:portal_label",
+      "is_spawnable": false,
+      "is_summonable": true,
+      "is_experimental": false
+    },
+    "components": {
+      "minecraft:nameable": {},
+      "minecraft:type_family": { "family": ["portal_label", "inanimate"] },
+      "minecraft:health": { "value": 1, "max": 1 },
+      "minecraft:physics": { "has_collision": false, "has_gravity": false },
+      "minecraft:pushable": { "is_pushable": false, "is_pushable_by_piston": false },
+      "minecraft:damage_sensor": {
+        "triggers": [{ "deals_damage": false }]
+      },
+      "minecraft:fire_immune": {},
+      "minecraft:knockback_resistance": { "value": 1.0, "max": 1.0 },
+      "minecraft:persistent": {},
+      "minecraft:movement": { "value": 0 },
+      "minecraft:collision_box": { "width": 0.01, "height": 0.01 }
+    }
+  }
+}