M1c: weather, snap building, shelter, beds and regrowth

- Seeded weather (clear/cloudy/rain/storm, snow and blizzards on cold days
  and above the snowline), lightning, synthesised rain/wind/thunder sound
- Rain/snow particles stopped by roofs; wet ground, settled snow and wind
  via global shader uniforms
- Snap-together wood floor, wall, door, roof and gable with structural
  support, collapse and X to dismantle
- Shelter detection: dry under a roof, warmer and Rested inside with a fire;
  rain burns an uncovered campfire faster
- Bed sets the spawn point and lets you sleep through the night
- Trees, boulders and ground pickups regrow; timers saved
- Grass cleared under floors; shorter HUD hint
- New test_weather_building suite (62 checks) and tests/run_all.sh, which
  also fails on script errors

data/items.json

@@ -191,6 +191,81 @@
           1.6
         ]
       }
+    },
+    {
+      "id": "wood_floor",
+      "name": "Wood Floor",
+      "category": "building",
+      "stack": 20,
+      "description": "2 x 2 m. Snaps to other pieces. Sits level on the ground.",
+      "mesh": "wood_floor",
+      "place": {
+        "piece": "build",
+        "kind": "floor"
+      }
+    },
+    {
+      "id": "wood_wall",
+      "name": "Wood Wall",
+      "category": "building",
+      "stack": 20,
+      "description": "2 x 2 m. Snaps to floor edges, other walls and roofs.",
+      "mesh": "wood_wall",
+      "place": {
+        "piece": "build",
+        "kind": "wall"
+      }
+    },
+    {
+      "id": "wood_door",
+      "name": "Wood Door",
+      "category": "building",
+      "stack": 10,
+      "description": "A wall with a door in it. E opens and closes it.",
+      "mesh": "wood_door",
+      "place": {
+        "piece": "door",
+        "kind": "door"
+      }
+    },
+    {
+      "id": "wood_roof",
+      "name": "Wood Roof",
+      "category": "building",
+      "stack": 20,
+      "description": "Rises 1 m over 2 m. Two from opposite walls of a 4 m hut meet at the ridge.",
+      "mesh": "wood_roof",
+      "place": {
+        "piece": "build",
+        "kind": "roof"
+      }
+    },
+    {
+      "id": "wood_gable",
+      "name": "Wood Gable",
+      "category": "building",
+      "stack": 20,
+      "description": "Triangle that closes the end of a roof. R to flip it.",
+      "mesh": "wood_gable",
+      "place": {
+        "piece": "build",
+        "kind": "gable"
+      }
+    },
+    {
+      "id": "bed",
+      "name": "Bed",
+      "category": "placeable",
+      "stack": 1,
+      "description": "Sets your spawn point. Sleep through the night under a roof.",
+      "mesh": "bed",
+      "place": {
+        "piece": "bed",
+        "footprint": [
+          1.0,
+          2.1
+        ]
+      }
     }
   ]
 }