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

project.godot

@@ -64,6 +64,21 @@ jump={
 
 common/physics_ticks_per_second=30
 
+[shader_globals]
+
+weather_wet={
+"type": "float",
+"value": 0.0
+}
+weather_snow={
+"type": "float",
+"value": 0.0
+}
+weather_wind={
+"type": "float",
+"value": 1.0
+}
+
 [rendering]
 
 lights_and_shadows/directional_shadow/size=8192