feat(M01): add explicit streaming focus

Work-Package: M01-RND-STREAMING-FOCUS-001

Agent: sindo-main-codex

src/domain/streaming/streaming_focus.gd

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+class_name StreamingFocus
+extends RefCounted
+
+## Immutable world-streaming point independent of cameras and the scene tree.
+## Renderer adapters may obtain this position from a player, spectator, editor
+## viewport or capture tool, but streaming consumers receive only this value.
+
+var world_position: GodotWorldPosition:
+	get:
+		return _world_position
+
+var _world_position: GodotWorldPosition
+
+
+## Creates a focus at an explicit position in the Godot renderer basis.
+func _init(world_position_value: GodotWorldPosition) -> void:
+	_world_position = world_position_value

src/domain/streaming/streaming_focus.gd.uid

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+uid://ehv78jvge0q2