feat(M03): add environment snapshot facade

src/render/environment/world_environment_snapshot.gd

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+class_name WorldEnvironmentSnapshot
+extends RefCounted
+
+## Immutable renderer input describing the authoritative time within one world day.
+## DBC light, area, fog and skybox selection remain owned by the sky controller.
+
+const HOURS_PER_DAY := 24.0
+const SCRIPT_PATH := "res://src/render/environment/world_environment_snapshot.gd"
+
+var is_valid: bool:
+	get:
+		return _is_valid
+
+var time_of_day_hours: float:
+	get:
+		return _time_of_day_hours
+
+var failure_code: StringName:
+	get:
+		return _failure_code
+
+var _is_valid: bool
+var _time_of_day_hours: float
+var _failure_code: StringName
+
+
+## Creates a snapshot and normalizes finite input into the half-open [0, 24) day.
+## Non-finite input produces an explicit invalid value instead of renderer state.
+static func at_time_of_day(time_of_day_hours_value: float) -> RefCounted:
+	return load(SCRIPT_PATH).new(time_of_day_hours_value)
+
+
+func _init(time_of_day_hours_value: float) -> void:
+	_is_valid = is_finite(time_of_day_hours_value)
+	_time_of_day_hours = (
+		fposmod(time_of_day_hours_value, HOURS_PER_DAY)
+		if _is_valid
+		else 0.0
+	)
+	_failure_code = &"" if _is_valid else &"environment_time_not_finite"

src/render/environment/world_environment_snapshot.gd.uid

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+uid://dass4mi3ex2fu