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/player/hands.gd

@@ -11,6 +11,7 @@ extends Node3D
 signal prompt_changed(text: String)
 
 const Campfire = preload("res://scripts/building/campfire.gd")
+const BuildPiece = preload("res://scripts/building/build_piece.gd")
 const REACH := 3.2
 const PLACE_REACH := 6.0
 const SWING_TIME := 0.5
@@ -26,6 +27,7 @@ var _ghost_bad_mat: StandardMaterial3D
 var _ghost_yaw := 0.0
 var _place_xf := Transform3D()
 var _place_ok := false
+var _place_reason := ""
 var _prompt := ""
 var _held_shown := "~"
 var _torch_light: OmniLight3D
@@ -123,6 +125,8 @@ func _target() -> Object:
 	if not _ray.is_colliding():
 		return null
 	var c := _ray.get_collider()
+	if c != null and c.has_meta("owner_piece"):
+		c = c.get_meta("owner_piece")   # a door's moving panel
 	if c == null or not c.has_method("interact_prompt"):
 		return null
 	if c.get("depleted") == true:
@@ -138,7 +142,8 @@ func _physics_process(delta: float) -> void:
 	var def := _held_def()
 	if def.has("place"):
 		_update_ghost(def)
-		_set_prompt("[LMB] Place %s   [R] Rotate" % def.name)
+		var why := "" if _place_ok or _place_reason.is_empty() else "   (%s)" % _place_reason
+		_set_prompt("[LMB] Place %s   [R] Rotate%s" % [def.name, why])
 		return
 	_ghost.visible = false
 	if _torch_light.visible:
@@ -146,7 +151,10 @@ func _physics_process(delta: float) -> void:
 		_torch_light.light_energy = float(def.get("light", {}).get("energy", 1.5)) * (0.85 + 0.15 * sin(_t * 17.0) * sin(_t * 5.3))
 	var t := _target()
 	if t != null:
-		_set_prompt(t.interact_prompt(player))
+		var p: String = t.interact_prompt(player)
+		if t.is_in_group("piece") and t.item_id != "grave":
+			p += "   [X] Dismantle"
+		_set_prompt(p)
 	elif def.has("food"):
 		_set_prompt("[RMB] Eat %s" % def.name)
 	else:
@@ -163,8 +171,16 @@ func _update_ghost(def: Dictionary) -> void:
 		_place_ok = false
 		return
 	var yaw := player.rotation.y + _ghost_yaw   # piece's front (+Z) faces the player
-	_place_xf = Transform3D(Basis(Vector3.UP, yaw), hit.position)
-	_place_ok = player.get_parent().placement_valid(def, _place_xf)
+	if BuildPiece.is_build(def):
+		# Building pieces snap to what's already built (build_system.gd).
+		var res: Dictionary = player.get_parent().build.placement(def, hit, yaw)
+		_place_xf = res.xf
+		_place_ok = res.ok
+		_place_reason = res.reason
+	else:
+		_place_xf = Transform3D(Basis(Vector3.UP, yaw), hit.position)
+		_place_ok = player.get_parent().placement_valid(def, _place_xf)
+		_place_reason = "" if _place_ok else "blocked or too steep"
 	_ghost.global_transform = _place_xf
 	_ghost.material_override = _ghost_ok_mat if _place_ok else _ghost_bad_mat
 	_ghost.visible = true
@@ -185,7 +201,12 @@ func _unhandled_input(event: InputEvent) -> void:
 		if _held_def().has("food"):
 			Actions.eat(player, player.selected)
 	elif event.is_action_pressed("rotate_piece"):
-		_ghost_yaw += deg_to_rad(22.5)
+		# Building pieces turn in quarter turns (they snap to a grid).
+		_ghost_yaw += deg_to_rad(90.0 if BuildPiece.is_build(_held_def()) else 22.5)
+	elif event.is_action_pressed("dismantle"):
+		var t := _target()
+		if t != null and t.is_in_group("piece"):
+			Actions.dismantle(player, t)
 	elif event.is_action_pressed("interact"):
 		var t := _target()
 		if t != null and t.has_method("interact"):