refactor: 把 /derivatives 的多源编排从 controller 搬进 usecase

为什么：原 controller handler 在 HTTP 层同时承担了 4 项 usecase 职责
（多源拼装、错误降级策略、limit 硬编码、响应结构组装），违反了
"controller 只做参数解析 + 调用 + 序列化" 的边界。等后续给衍生品加
缓存 / taker volume / 数据质量字段时，HTTP 层会持续变厚。

改动：
- 新增 internal/usecase/market_query.go: MarketQueryUsecase.GetDerivatives()
  并发拉 current funding/OI + 串行查历史 + 错误聚合为 warnings 返回
- /derivatives handler 退化到 4 行；MarketDeps / restapi.Deps 同步收窄
- /klines 保持直查 KlineRepo（thin query，G11 例外）
- 新增 G11 守卫：grep "FundingRepo|OIRepo|LSRepo|TakerRepo" internal/controller

破坏性 API 变更（/derivatives 响应）：
- 删除 funding.error / openInterest.error
- 新增顶层 warnings: []string
顶层 symbol / funding / openInterest / longShortRatio / takerBuySellVolume 保持。

harness 同步：
- AGENTS.md §6 加 G11 grep
- ai/project-map.md 加 market_query.go + /derivatives 数据流分支
- ai/task-templates.md T6 加"破坏性变体"分支（本次重构暴露了原假设过严）
- ai/harness-health.md W1 记一次轻量验证 + 守卫数 10→11

验收: go build / go vet / G6 grep / G11 grep 全绿。

internal/usecase/market_query.go

@@ -0,0 +1,113 @@
+package usecase
+
+import (
+	"context"
+	"sync"
+
+	"golang.org/x/sync/errgroup"
+
+	"cryptoHermes/internal/entity"
+)
+
+const (
+	derivativesFundingHistoryLen = 100
+	derivativesOIHistoryLen      = 200
+	derivativesLongShortLen      = 200
+)
+
+type MarketQueryUsecase struct {
+	derivatives DerivativesProvider
+	fundingRepo FundingRepository
+	oiRepo      OpenInterestRepository
+	lsRepo      LongShortRatioRepository
+}
+
+func NewMarketQueryUsecase(
+	derivatives DerivativesProvider,
+	fundingRepo FundingRepository,
+	oiRepo OpenInterestRepository,
+	lsRepo LongShortRatioRepository,
+) *MarketQueryUsecase {
+	return &MarketQueryUsecase{
+		derivatives: derivatives,
+		fundingRepo: fundingRepo,
+		oiRepo:      oiRepo,
+		lsRepo:      lsRepo,
+	}
+}
+
+func (u *MarketQueryUsecase) GetDerivatives(ctx context.Context, symbol, period string) (*entity.DerivativesBundle, []string, error) {
+	var (
+		currentFund *entity.FundingRate
+		currentOI   *entity.OpenInterest
+		warnMu      sync.Mutex
+		warnings    []string
+	)
+	addWarn := func(w string) {
+		warnMu.Lock()
+		warnings = append(warnings, w)
+		warnMu.Unlock()
+	}
+
+	g, gctx := errgroup.WithContext(ctx)
+	g.Go(func() error {
+		f, err := u.derivatives.GetCurrentFunding(gctx, symbol)
+		if err != nil {
+			addWarn("current funding fetch failed: " + err.Error())
+			return nil
+		}
+		currentFund = f
+		return nil
+	})
+	g.Go(func() error {
+		oi, err := u.derivatives.GetCurrentOpenInterest(gctx, symbol)
+		if err != nil {
+			addWarn("current OI fetch failed: " + err.Error())
+			return nil
+		}
+		currentOI = oi
+		return nil
+	})
+	_ = g.Wait()
+
+	fundingHist, err := u.fundingRepo.FindRecent(ctx, symbol, derivativesFundingHistoryLen)
+	if err != nil {
+		addWarn("funding history query failed: " + err.Error())
+	}
+
+	oiHist, err := u.oiRepo.FindRecent(ctx, symbol, period, derivativesOIHistoryLen)
+	if err != nil {
+		addWarn("OI history query failed: " + err.Error())
+	}
+
+	globalLS, err := u.lsRepo.FindRecent(ctx, symbol, period, entity.RatioTypeGlobalAccount, derivativesLongShortLen)
+	if err != nil {
+		addWarn("global long/short query failed: " + err.Error())
+	}
+
+	topLS, err := u.lsRepo.FindRecent(ctx, symbol, period, entity.RatioTypeTopTraderPosition, derivativesLongShortLen)
+	if err != nil {
+		addWarn("top trader position long/short query failed: " + err.Error())
+	}
+
+	bundle := &entity.DerivativesBundle{
+		Funding: entity.FundingBundle{
+			Current: currentFund,
+			History: fundingHist,
+		},
+		OpenInterest: entity.OpenInterestBundle{
+			Current: currentOI,
+			History: oiHist,
+		},
+		LongShortRatio: entity.LongShortBundle{
+			Global:            globalLS,
+			TopTraderPosition: topLS,
+		},
+		TakerBuySellVolume: []entity.TakerBuySellVolume{},
+	}
+
+	if warnings == nil {
+		warnings = []string{}
+	}
+	return bundle, warnings, nil
+}