Move layout reload policy into platform api

src/platform_api/asset_file_load_policy.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <cstdint>
+#include <string_view>
+
+namespace pp::platform {
+
+struct AssetFileLoadDecision {
+    bool should_read_file = true;
+    bool skipped_load_result = true;
+    std::int64_t last_write_time = 0;
+};
+
+[[nodiscard]] AssetFileLoadDecision plan_asset_file_load(
+    std::string_view absolute_path,
+    bool already_loaded,
+    std::int64_t previous_last_write_time);
+
+}