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>

tow-boat-addon/tow_boat_BP/entities/tow_boat.json

@@ -0,0 +1,95 @@
+{
+  "format_version": "1.21.0",
+  "minecraft:entity": {
+    "description": {
+      "identifier": "silverlabs:tow_boat",
+      "is_spawnable": false,
+      "is_summonable": true,
+      "is_experimental": false
+    },
+    "components": {
+      "minecraft:type_family": {
+        "family": ["tow_boat", "boat"]
+      },
+      "minecraft:health": {
+        "value": 20,
+        "max": 20
+      },
+      "minecraft:collision_box": {
+        "width": 1.4,
+        "height": 0.55
+      },
+      "minecraft:physics": {
+        "has_gravity": true,
+        "has_collision": true
+      },
+      "minecraft:pushable": {
+        "is_pushable": true,
+        "is_pushable_by_piston": false
+      },
+      "minecraft:persistent": {},
+      "minecraft:nameable": {},
+      "minecraft:movement": {
+        "value": 0.18
+      },
+      "minecraft:movement.basic": {},
+      "minecraft:navigation.float": {
+        "can_path_over_water": true,
+        "can_breach": false
+      },
+      "minecraft:underwater_movement": {
+        "value": 0.0
+      },
+      "minecraft:can_climb": {},
+      "minecraft:rideable": {
+        "seat_count": 1,
+        "family_types": ["player"],
+        "interact_text": "action.interact.mount",
+        "pull_in_entities": false,
+        "seats": [
+          {
+            "position": [0, 0.4, 0.0],
+            "lock_rider_rotation": 90,
+            "min_rider_count": 0,
+            "max_rider_count": 1
+          }
+        ]
+      },
+      "minecraft:input_ground_controlled": {},
+      "minecraft:leashable": {
+        "soft_distance": 4.0,
+        "hard_distance": 6.0,
+        "max_distance": 12.0
+      },
+      "minecraft:damage_sensor": {
+        "triggers": [
+          {
+            "cause": "drowning",
+            "deals_damage": "no"
+          },
+          {
+            "cause": "fall",
+            "deals_damage": "no"
+          },
+          {
+            "cause": "fire",
+            "deals_damage": "no"
+          },
+          {
+            "cause": "fire_tick",
+            "deals_damage": "no"
+          },
+          {
+            "cause": "lava",
+            "deals_damage": "no"
+          },
+          {
+            "cause": "suffocation",
+            "deals_damage": "no"
+          }
+        ]
+      }
+    },
+    "events": {}
+  }
+}