Replace MPQ runtime with loose file asset system

Extract assets from MPQ archives into organized loose files indexed by
manifest.json, enabling fully parallel reads without StormLib serialization.
Add asset_extract and blp_convert tools, PNG texture override support.

include/pipeline/loose_file_reader.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <cstdint>
+
+namespace wowee {
+namespace pipeline {
+
+/**
+ * LooseFileReader - Thread-safe filesystem file reader
+ *
+ * Each read opens its own file descriptor, so no mutex is needed.
+ * This replaces the serialized MPQ read path.
+ */
+class LooseFileReader {
+public:
+    LooseFileReader() = default;
+
+    /**
+     * Read entire file into memory
+     * @param filesystemPath Full path to file on disk
+     * @return File contents (empty if not found or error)
+     */
+    static std::vector<uint8_t> readFile(const std::string& filesystemPath);
+
+    /**
+     * Check if a file exists on disk
+     */
+    static bool fileExists(const std::string& filesystemPath);
+
+    /**
+     * Get file size without reading
+     * @return Size in bytes, or 0 if not found
+     */
+    static uint64_t getFileSize(const std::string& filesystemPath);
+};
+
+} // namespace pipeline
+} // namespace wowee