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

scripts/ui/pause_menu.gd

@@ -9,7 +9,9 @@ const CONTROLS := [
 	["W A S D", "Move"], ["Shift", "Sprint"], ["Space", "Jump / swim up"],
 	["Mouse", "Look"], ["E", "Interact / pick up / add fuel"], ["Left click", "Use tool / place"],
 	["Right click (holding food)", "Eat"],
-	["R", "Rotate piece"], ["1 - 8, wheel", "Hotbar"], ["Tab", "Inventory & crafting"],
+	["R", "Rotate piece (building pieces: quarter turns)"], ["X", "Dismantle the piece you're looking at"],
+	["E on a bed", "Set spawn point / sleep (night, under a roof)"],
+	["1 - 8, wheel", "Hotbar"], ["Tab", "Inventory & crafting (shift-click Craft for 5)"],
 	["Shift + click", "Move stack to/from a chest"], ["Right click", "Split stack"],
 	["Esc", "This menu (game autosaves every 2 min)"],
 ]