feat(compute): 添加 qwen3.8-max-preview 模型 (#66)

- 新增 Qwen3.8-Max Preview 到 dashscope provider 和 model-specs
- 100万上下文，支持视觉理解（serviceType 含 vision）、Agent、推理
- supportsReasoning: true
- 定价：输入 ¥12/M token，输出 ¥36/M token
- presetDataVersion 81 → 82

compute/providers/dashscope.json

@@ -33,6 +33,32 @@
     "qwen3-max-trans"
   ],
   "models": [
+    {
+      "modelName": "qwen3.8-max-preview",
+      "displayName": "阿里云 Qwen3.8-Max (Preview)",
+      "serviceType": [
+        "chat",
+        "vision"
+      ],
+      "description": "通义千问3.8 Max 预览版，面向复杂推理与长程 Agent 任务的旗舰模型，100万上下文，支持视觉理解、内置工具和 Function Calling",
+      "contextWindow": 1000000,
+      "maxOutputTokens": 65536,
+      "capabilities": [
+        "chat",
+        "reasoning",
+        "code",
+        "multilingual",
+        "long_context",
+        "tool_use",
+        "agent",
+        "vision"
+      ],
+      "inputPrice": 12,
+      "outputPrice": 36,
+      "defaultTemperature": 0.6,
+      "defaultTopP": 0.95,
+      "extra": {}
+    },
     {
       "modelName": "qwen3.7-max",
       "displayName": "阿里云 Qwen3.7-Max",