New Components/ Prepare to new scene loading system

utilities/AsyncFilePreloader.h

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+#pragma once
+#include <string>
+#include <vector>
+#include <memory>
+#include <unordered_map>
+#include <unordered_set>
+#include <mutex>
+#include <condition_variable>
+#include <thread>
+#include <queue>
+#include <atomic>
+
+// Thread pool that reads files from disk into memory so the main thread can
+// skip disk I/O and parse directly from RAM.  Only covers the binary path
+// (E3D); text models fall back to synchronous load.
+class AsyncFilePreloader {
+public:
+    using Buffer = std::shared_ptr<std::vector<char>>;
+
+    AsyncFilePreloader() = default;
+    ~AsyncFilePreloader() { stop(); }
+
+    AsyncFilePreloader(const AsyncFilePreloader&) = delete;
+    AsyncFilePreloader& operator=(const AsyncFilePreloader&) = delete;
+
+    // Start N worker threads (clamped to [1, hardware_concurrency]).
+    void start(int thread_count = 0);
+
+    // Signal workers to stop and join them.  Clears the queue but keeps
+    // already-loaded buffers so late callers still get cache hits.
+    void stop();
+
+    // Queue a file for background loading.  Silently skips duplicates.
+    void queue(std::string path);
+
+    // Return the preloaded buffer for `path`, or nullptr if not ready yet.
+    // Does NOT block — callers must fall back to synchronous I/O if nullptr.
+    Buffer get(const std::string& path) const;
+
+    // Drop all cached buffers (call after loading finishes to free memory).
+    void clear();
+
+    bool is_running() const { return m_running.load(std::memory_order_relaxed); }
+
+private:
+    void worker();
+
+    mutable std::mutex          m_mutex;
+    std::condition_variable     m_cv;
+    std::queue<std::string>     m_pending;
+    std::unordered_set<std::string> m_queued;  // prevents duplicate queuing
+    std::unordered_map<std::string, Buffer> m_cache;
+    std::vector<std::thread>    m_workers;
+    std::atomic<bool>           m_running { false };
+};
+
+extern AsyncFilePreloader GModelPreloader;