Migration: client.query -> defineQuery/observeQuery

迁移目标

把“定义缓存”和“订阅视图”分开：

• 缓存级：defineQuery（key/queryFn/stale/retry/gc）
• 观察者级：observeQuery（enabled/select/placeholder/refetchOn*）

基础迁移

之前

const user = client.query({
  key: ['user', id],
  queryFn: ({ signal }) => fetchUser(id, signal),
});

await user.fetch();

之后

const userQuery = client.defineQuery({
  key: ['user', id],
  queryFn: ({ signal }) => fetchUser(id, signal),
});

const userObserver = client.observeQuery({
  query: userQuery,
  enabled: true,
  refetchOnMount: 'stale',
});

await userQuery.fetch();

批量操作迁移

• invalidateQueries：保留
• cancelQueries：保留
• removeQueries：保留
• 新增：refetchQueries、resetQueries、setQueriesData

SSR 迁移

const dehydrated = client.dehydrate();
client.hydrate(dehydrated);

React 侧最小迁移

useQuery 调用方式保持接近，但建议显式传 query 句柄以消除定义歧义：

const userQuery = client.defineQuery({
  key: ['user', id],
  queryFn: ({ signal }) => fetchUser(id, signal),
});

const user = useQuery({
  client,
  query: userQuery,
  select: (value) => value,
});