render: add M2 build resource snapshot

src/render/m2/m2_build_resource_snapshot.gd

@@ -0,0 +1,72 @@
+class_name M2BuildResourceSnapshot
+extends RefCounted
+
+## Holds one M2 build-step resource observation without owning engine lifetime.
+
+var _normalized_relative_path: String
+var _animated_prototype: Node3D
+var _animation_request_pending: bool
+var _static_mesh: Mesh = null
+var _static_model_missing: bool = false
+
+
+func _init(
+	normalized_relative_path: String,
+	animated_prototype: Node3D,
+	animation_request_pending: bool
+) -> void:
+	_normalized_relative_path = normalized_relative_path
+	_animated_prototype = animated_prototype
+	_animation_request_pending = animation_request_pending
+
+
+## Returns the normalized M2 path observed by the loader.
+func normalized_relative_path() -> String:
+	return _normalized_relative_path
+
+
+## Returns the borrowed animated prototype without transferring ownership.
+func animated_prototype() -> Node3D:
+	return _animated_prototype
+
+
+## Returns whether an animated prototype was observed.
+func has_animated_prototype() -> bool:
+	return _animated_prototype != null
+
+
+## Returns whether the animation request remains pending.
+func animation_request_pending() -> bool:
+	return _animation_request_pending
+
+
+## Adopts the optional static Mesh and terminal missing-model observation.
+func adopt_static_observation(static_mesh: Mesh, static_model_missing: bool) -> void:
+	_static_mesh = static_mesh
+	_static_model_missing = static_model_missing
+
+
+## Returns the borrowed static Mesh without transferring ownership.
+func static_mesh() -> Mesh:
+	return _static_mesh
+
+
+## Returns whether a prepared static Mesh was observed.
+func has_static_mesh() -> bool:
+	return _static_mesh != null
+
+
+## Returns whether the static model lookup reached a terminal missing outcome.
+func static_model_missing() -> bool:
+	return _static_model_missing
+
+
+## Returns detached path/availability diagnostics without engine references.
+func diagnostic_snapshot() -> Dictionary:
+	return {
+		"normalized_relative_path": _normalized_relative_path,
+		"has_animated_prototype": has_animated_prototype(),
+		"animation_request_pending": _animation_request_pending,
+		"has_static_mesh": has_static_mesh(),
+		"static_model_missing": _static_model_missing,
+	}