feat: full format compatibility adaptation for model downloads

- Add get_model_urls() and download_model() to api.py and api_complete.py
  supporting all 14 discovered urlResult format keys (glb, obj, pbr maps, etc.)
- Update generator.py to extract full urlResult dict instead of just modelUrl
- Add CLI subcommands: formats (list available formats) and download (fetch by key)
- Update reverse engineering docs with complete format key table and CLI examples

hunyuan3dweb/api.py

@@ -7,7 +7,9 @@
 import requests
 import json
 import time
+import os
 from typing import Optional, Dict, Any
+from urllib.parse import urlparse, unquote
 from .sign import sign, sign_with_custom_nonce
 
 BASE_URL = "https://3d.hunyuan.tencent.com"
@@ -17,6 +19,24 @@ API_BASE = f"{BASE_URL}/api/3d"
 class Hunyuan3DAPI:
     """腾讯混元3D API客户端"""
 
+    # 模型下载格式键名（与腾讯混元3D API返回的 urlResult 字段对应）
+    MODEL_FORMAT_KEYS = [
+        "glb",          # 带PBR贴图的GLB二进制模型
+        "obj",          # OBJ模型（通常打包在zip中）
+        "mtl",          # MTL材质文件
+        "obj_url",      # 独立OBJ文件URL
+        "geometryGlb",  # 纯几何GLB（无材质）
+        "textureGlb",   # GLB纹理
+        "textureObj",   # OBJ纹理包
+        "image_url",    # 预览图/缩略图
+        "pbrImage",           # PBR综合贴图
+        "pbrMetallicImage",   # PBR金属度贴图
+        "pbrRoughnessImage",  # PBR粗糙度贴图
+        "pbrNormalImage",     # PBR法线贴图
+        "invisible_wall",     # 不可见碰撞墙
+        "air_wall",           # 空气墙（碰撞体）
+    ]
+
     def __init__(self, cookies: Optional[str] = None):
         """
         初始化API客户端
@@ -180,6 +200,66 @@ class Hunyuan3DAPI:
             "creationsId": creation_id
         })
 
+    def get_model_urls(self, creation_id: str) -> Dict[str, Optional[str]]:
+        """
+        获取指定创作所有可用格式的下载URL
+
+        Returns:
+            格式键名 -> 下载URL 的字典，空值已被过滤
+        """
+        status = self.get_generation_status(creation_id)
+
+        # 兼容两种响应包装格式
+        if "code" in status:
+            data = status.get("data", {})
+        else:
+            data = status
+
+        result_list = data.get("result", [])
+        if not result_list:
+            return {}
+
+        url_result = result_list[0].get("urlResult", {})
+        return {
+            key: val
+            for key in self.MODEL_FORMAT_KEYS
+            if (val := url_result.get(key)) and val not in (None, "", {})
+        }
+
+    def download_model(self, creation_id: str, format_key: str = "glb",
+                       output_path: Optional[str] = None) -> str:
+        """
+        下载指定格式的模型文件
+
+        Args:
+            creation_id: 创作ID
+            format_key: 格式键名，如 'glb' / 'obj' / 'pbrNormalImage' 等
+            output_path: 本地保存路径，为空时自动从URL推断文件名
+
+        Returns:
+            实际保存的本地文件路径
+        """
+        urls = self.get_model_urls(creation_id)
+        if format_key not in urls:
+            available = ", ".join(urls.keys())
+            raise ValueError(
+                f"格式 '{format_key}' 不可用。可用格式: {available}"
+            )
+
+        url = urls[format_key]
+        resp = self.session.get(url, timeout=120)
+        resp.raise_for_status()
+
+        if output_path is None:
+            parsed = urlparse(url)
+            filename = unquote(os.path.basename(parsed.path)) or f"{creation_id}_{format_key}"
+            output_path = filename
+
+        with open(output_path, "wb") as f:
+            f.write(resp.content)
+
+        return os.path.abspath(output_path)
+
     def wait_for_completion(self, creation_id: str, timeout: int = 600,
                            poll_interval: int = 5) -> Dict[str, Any]:
         """