feat(M01): add explicit streaming focus

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

Agent: sindo-main-codex

src/tools/probe_render_terrain_height.gd

@@ -36,7 +36,7 @@ func _run_async() -> void:
 	var camera := Camera3D.new()
 	camera.current = true
 	world.add_child(camera)
-	world.set("camera_path", NodePath(camera.name))
+	world.set("streaming_focus_source_path", NodePath(camera.name))
 	world.set("debug_streaming", false)
 	get_root().add_child(world)
 	await process_frame
@@ -53,8 +53,8 @@ func _run_async() -> void:
 			continue
 		var camera_position := _vector3(checkpoint.get("camera", []))
 		camera.global_position = camera_position
-		if world.has_method("_refresh_streaming_targets_at"):
-			world.call("_refresh_streaming_targets_at", camera_position, true)
+		if world.has_method("refresh_streaming_focus"):
+			world.call("refresh_streaming_focus", true)
 		await create_timer(maxf(0.1, wait_seconds)).timeout
 		var terrain_sample := _sample_terrain(world, camera_position)
 		terrain_sample["name"] = checkpoint.get("name", "checkpoint")