Add derivatives tool, trim provider fields, widen model call retries

- New chat tool get_derivatives: funding rate (next estimate and recent
  settlements), premium, open interest change vs price, global and top
  trader long/short ratios, taker buy/sell ratio from Binance public
  endpoints. Each part fails independently.
- Strip whitespace from provider name and model; a leading space in the
  model name made the upstream return 404.
- Retry connection failures and mid-stream disconnects (raw httpx /
  httpx2 errors are not wrapped by the SDKs) up to 3 times while no
  output has been emitted, and surface them as chat errors.
- Return 30 recent bars from get_klines instead of 60 to cut tokens.

web/src/pages/chat/components/MessageList.vue

@@ -30,6 +30,7 @@ const TOOL_LABELS: Record<string, string> = {
   search_symbols: "查找交易对",
   get_klines: "获取 K 线",
   get_ticker: "获取 24h 行情",
+  get_derivatives: "获取衍生品数据",
   list_skills: "列出 skills",
   read_skill: "读取 skill",
   propose_skill_edit: "提交 skill 草稿",