feat(model-specs): 新增模型规格库——跨 provider 模型参数统一维护（presetDataVersion 54→58）

* feat(model-specs): 新增模型规格库与 schema 契约

- compute/model-specs/：按厂商维护模型内在参数（上下文窗口/最大输出/能力/serviceType/默认温度，不含价签）
- schemas/model-spec.schema.json：Draft-07 契约，spec 允许 null（新文件不影响老客户端 frozen 契约）
- scripts/validate.mjs：pickSchemaKey 纳入 model-specs 校验
- manifest.presetDataVersion 54→55

* feat(model-specs): 新增小米 MiMo 系列模型规格；bump presetDataVersion 55→56

* feat(model-specs): 补全全量模型规格；presetDataVersion 56→57

* feat(model-specs): 新增 releasedAt/retiredAt 时间戳字段；补充 mimo 退役日期

compute/model-specs/_index.json

@@ -0,0 +1,26 @@
+{
+  "description": "模型规格库加载顺序索引。元素为对应 JSON 文件的 basename（不含 .json）。",
+  "order": [
+    "anthropic",
+    "openai",
+    "google",
+    "deepseek",
+    "qwen",
+    "moonshot",
+    "zhipu",
+    "minimax",
+    "xai",
+    "mistral",
+    "xiaomi",
+    "baichuan",
+    "baidu",
+    "cohere",
+    "kling",
+    "lingyiwanwu",
+    "perplexity",
+    "stability",
+    "tencent",
+    "volcengine",
+    "xunfei"
+  ]
+}