rnd(M03): introduce renderer facade seam

Work-Package: M03-RND-FACADE-001
Agent: sindo-main-codex
Tests: facade/focus/coordinate/manifest contracts, renderer dry-run, coordination and documentation gates
Fidelity: focus targets, budgets, queues, caches and visible renderer behavior remain unchanged

src/render/world_render_facade.gd

@@ -0,0 +1,110 @@
+@tool
+class_name WorldRenderFacade
+extends Node
+
+## Stable main-thread boundary between runtime/tool callers and the monolithic
+## streaming renderer. The facade owns no queues, caches, nodes or RIDs.
+
+const GODOT_WORLD_POSITION_SCRIPT := preload("res://src/domain/coordinates/godot_world_position.gd")
+const STREAMING_FOCUS_SCRIPT := preload("res://src/domain/streaming/streaming_focus.gd")
+
+## Internal renderer implementation resolved relative to this node.
+## The referenced node remains owned by its scene parent.
+@export var streaming_world_loader_path: NodePath = NodePath("..")
+
+## Optional explicit Node3D source sampled in Godot world coordinates.
+## Runtime scenes use the player; capture and probe tools replace it with their camera.
+@export var streaming_focus_source_path: NodePath
+
+var _streaming_world_loader: Node
+var _missing_loader_reported := false
+var _missing_focus_source_reported := false
+
+
+func _ready() -> void:
+	_resolve_streaming_world_loader()
+	set_process(streaming_focus_source_path != NodePath())
+	if streaming_focus_source_path != NodePath():
+		# Child nodes become ready before their parent StreamingWorldLoader. Only
+		# publish the initial focus here; the loader applies it after initialization.
+		_capture_streaming_focus_from_source()
+
+
+func _process(_delta_seconds: float) -> void:
+	_capture_streaming_focus_from_source()
+
+
+## Replaces the renderer focus. The immutable value remains caller-owned; the
+## internal streamer retains the reference for its next throttled refresh.
+func set_streaming_focus(streaming_focus: StreamingFocus) -> void:
+	var loader := _resolve_streaming_world_loader()
+	if loader == null:
+		return
+	loader.call("set_streaming_focus", streaming_focus)
+
+
+## Samples the configured source and requests target refresh from the internal
+## streamer. Returns false when either dependency or a valid focus is unavailable.
+func refresh_streaming_focus(force: bool = false) -> bool:
+	_capture_streaming_focus_from_source()
+	var loader := _resolve_streaming_world_loader()
+	if loader == null:
+		return false
+	return bool(loader.call("refresh_streaming_focus", force))
+
+
+## Returns a detached read-only metrics snapshot for diagnostics and baselines.
+## Mutating the returned Dictionary cannot mutate renderer-owned state.
+func renderer_metrics_snapshot() -> Dictionary:
+	var loader := _resolve_streaming_world_loader()
+	if loader == null:
+		return {}
+	var metrics_variant = loader.call("render_baseline_snapshot")
+	if not (metrics_variant is Dictionary):
+		push_error("WorldRenderFacade received a non-Dictionary renderer metrics snapshot.")
+		return {}
+	return (metrics_variant as Dictionary).duplicate(true)
+
+
+func _capture_streaming_focus_from_source() -> void:
+	if streaming_focus_source_path == NodePath():
+		return
+	var focus_source := get_node_or_null(streaming_focus_source_path) as Node3D
+	if focus_source == null:
+		if not _missing_focus_source_reported:
+			push_warning("WorldRenderFacade focus source is missing or is not Node3D: %s" % streaming_focus_source_path)
+			_missing_focus_source_reported = true
+		return
+
+	_missing_focus_source_reported = false
+	var godot_position: Vector3 = focus_source.global_position
+	var typed_world_position = GODOT_WORLD_POSITION_SCRIPT.new(
+		godot_position.x,
+		godot_position.y,
+		godot_position.z
+	)
+	set_streaming_focus(STREAMING_FOCUS_SCRIPT.new(typed_world_position))
+
+
+func _resolve_streaming_world_loader() -> Node:
+	if is_instance_valid(_streaming_world_loader):
+		return _streaming_world_loader
+	var candidate := get_node_or_null(streaming_world_loader_path)
+	if candidate == null:
+		if not _missing_loader_reported:
+			push_error("WorldRenderFacade cannot resolve StreamingWorldLoader at %s" % streaming_world_loader_path)
+			_missing_loader_reported = true
+		return null
+	for required_method in [
+		&"set_streaming_focus",
+		&"refresh_streaming_focus",
+		&"render_baseline_snapshot",
+	]:
+		if not candidate.has_method(required_method):
+			if not _missing_loader_reported:
+				push_error("WorldRenderFacade renderer implementation lacks %s" % required_method)
+				_missing_loader_reported = true
+			return null
+	_streaming_world_loader = candidate
+	_missing_loader_reported = false
+	return _streaming_world_loader

src/render/world_render_facade.gd.uid

@@ -0,0 +1 @@
+uid://sxn3ai2ic18r