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/asset_manifest.hpp

@@ -0,0 +1,74 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <cstdint>
+#include <unordered_map>
+
+namespace wowee {
+namespace pipeline {
+
+/**
+ * AssetManifest - Maps WoW virtual paths to filesystem paths
+ *
+ * Loaded once at startup from manifest.json. Read-only after init,
+ * so concurrent reads are safe without a mutex.
+ */
+class AssetManifest {
+public:
+    struct Entry {
+        std::string filesystemPath;  // Relative path from basePath (forward slashes)
+        uint64_t size;               // File size in bytes
+        uint32_t crc32;              // CRC32 for integrity verification
+    };
+
+    AssetManifest() = default;
+
+    /**
+     * Load manifest from JSON file
+     * @param manifestPath Full path to manifest.json
+     * @return true if loaded successfully
+     */
+    bool load(const std::string& manifestPath);
+
+    /**
+     * Lookup an entry by normalized WoW path (lowercase, backslash)
+     * @return Pointer to entry or nullptr if not found
+     */
+    const Entry* lookup(const std::string& normalizedWowPath) const;
+
+    /**
+     * Resolve full filesystem path for a WoW virtual path
+     * @return Full filesystem path or empty string if not found
+     */
+    std::string resolveFilesystemPath(const std::string& normalizedWowPath) const;
+
+    /**
+     * Check if an entry exists
+     */
+    bool hasEntry(const std::string& normalizedWowPath) const;
+
+    /**
+     * Get base path (directory containing extracted assets)
+     */
+    const std::string& getBasePath() const { return basePath_; }
+
+    /**
+     * Get total number of entries
+     */
+    size_t getEntryCount() const { return entries_.size(); }
+
+    /**
+     * Check if manifest is loaded
+     */
+    bool isLoaded() const { return loaded_; }
+
+private:
+    bool loaded_ = false;
+    std::string basePath_;           // Root directory for extracted assets
+    std::string manifestDir_;        // Directory containing manifest.json
+    std::unordered_map<std::string, Entry> entries_;
+};
+
+} // namespace pipeline
+} // namespace wowee