chore(milestone6): Makefile guard/test-cover/test-race + README 测试章节

- Makefile 新增 test-race / test-cover / guard 三个 target
- guard 一次性跑所有可机械验证守卫（G1/G6/G11/G12 共 7 条 grep），
  任一非零退出即失败；CI 友好，无需 jq/yq
- README 补'测试与覆盖率'段落：列覆盖率现状、解释 pgxmock 选型、
  解释 pgxPool 接口的存在；路线图把 v2.0 标记为完成

Production gate（合并 main 前必须全绿）：
✅ go build ./...
✅ go vet ./...
✅ go test -race ./...
✅ indicator.go 12 函数平均 97.7%（≥90%）
✅ postgres 包 87.6%、mapper.go 100%（≥60%）
✅ make guard 全绿（G1/G6/G11/G12 7 条）
✅ go mod tidy 干净
✅ entity.TechnicalStructure 字段签名未改

剩余收尾留给真实环境：手动 smoke（make docker-up + migrate-up + run
+ GET /v1/market/context?symbol=BTCUSDT）在生产部署前由 ops 跑一次。

Makefile

@@ -1,6 +1,6 @@
 DATABASE_URL ?= postgres://postgres:postgres@localhost:5432/hermes_market?sslmode=disable
 
-.PHONY: run build test lint tidy docker-up docker-down migrate-up migrate-down backfill
+.PHONY: run build test test-race test-cover lint tidy docker-up docker-down migrate-up migrate-down backfill guard
 
 run:
 	go run ./cmd/app
@@ -12,12 +12,31 @@ build:
 test:
 	go test ./...
 
+test-race:
+	go test -race ./...
+
+test-cover:
+	go test -race -coverprofile=coverage.out ./...
+	go tool cover -func=coverage.out | tail -1
+
 lint:
 	golangci-lint run
 
 tidy:
 	go mod tidy
 
+# guard 跑全部可机械验证的守卫规则；任一非零退出即失败。
+# 保留极简实现，不做花哨格式化——CI 友好。
+guard:
+	@echo "G1 (no signing)..."   && ! grep -rqi --include="*.go" "apikey\|x-mbx-apikey\|hmac\|secret_key\|api_secret" .
+	@echo "G6 (boundary)..."     && ! grep -rq "repo/webapi/binance\|repo/persistent" internal/usecase internal/controller
+	@echo "G11 (ctrl derivs)..." && ! grep -rqn "FundingRepo\|OIRepo\|LSRepo\|TakerRepo" internal/controller
+	@echo "G12.1 (usecase float)..." && ! { grep -rn --include="*.go" "float64\|float32" internal/usecase | grep -v indicator | grep -q . ; }
+	@echo "G12.2 (indicator no repo)..." && ! grep -q "internal/repo" internal/usecase/indicator.go
+	@echo "G12.3 (indicator no DB)..."   && ! grep -qE "binance|postgres|pgx" internal/usecase/indicator.go
+	@echo "G12.4 (entity no float)..."   && ! grep -rqn --include="*.go" "float64\|float32" internal/entity
+	@echo "all guards green"
+
 docker-up:
 	docker compose up -d