feat(assets): replace is_procedural/is_gpu_procedural bools with AssetType enum, add MP3 type

- Add AssetType enum {STATIC, PROC, PROC_GPU, MP3} to AssetRecord
- Add GetAssetType() API to asset_manager.h/cc
- asset_packer: parse 'MP3' compression keyword in assets.txt
- tracker: remove magic-byte is_mp3_asset(); use GetAssetType() instead
- assets.txt: NEVER_MP3 now uses 'MP3' compression type
- doc/ASSET_SYSTEM.md: rewritten to document new types and API

handoff(Gemini): AssetType enum landed; MP3 detection is now explicit via asset metadata.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/util/asset_manager.h b/src/util/asset_manager.h
index 1714c21..09483e5 100644
--- a/src/util/asset_manager.h
+++ b/src/util/asset_manager.h
@@ -5,12 +5,12 @@
 #pragma once
 #include "asset_manager_dcl.h"
 
+enum class AssetType : uint8_t { STATIC, PROC, PROC_GPU, MP3 };
+
 struct AssetRecord {
   const uint8_t* data; // Pointer to asset data (static or dynamic)
   size_t size;         // Size of the asset data
-  bool is_procedural;  // True if data was dynamically allocated by a procedural
-                       // generator
-  bool is_gpu_procedural; // True if GPU compute shader generates texture
+  AssetType type;
   const char* proc_func_name_str; // Name of procedural generation function
                                   // (string literal)
   const float* proc_params; // Parameters for procedural generation (static,
@@ -30,6 +30,9 @@ void DropAsset(AssetId asset_id, const uint8_t* asset);
 // found.
 AssetId GetAssetIdByName(const char* name);
 
+// Returns the AssetType for a given asset id.
+AssetType GetAssetType(AssetId asset_id);
+
 #if !defined(STRIP_ALL)
 // Hot-reload: Parse and reload assets from config file (debug only)
 bool ReloadAssetsFromFile(const char* config_path);