chore: 添加 CI 工具链 — golangci-lint + gofumpt + goimports + Makefile

.golangci.yml:
  - 启用 linter: errcheck, gosec, govet, staticcheck, ineffassign, unused,
    revive, contextcheck, errorlint, errname, misspell
  - 启用 formatter: gofumpt + goimports

Makefile:
  - fmt/fmt-check: gofumpt + goimports 格式检查
  - lint/lint-strict: golangci-lint 报告/阻断模式
  - test: go test -race
  - ci: 完整 CI 流程 (fmt-check + lint)

docs/code-style.md:
  - 新增 AI 执行协议 + 代码格式化/自动化检查/MUST规则
  - 集成 golangci-lint 检查项与规范对照

Makefile

@@ -0,0 +1,35 @@
+.PHONY: lint fmt check test
+
+# === 代码格式化 ===
+fmt:
+	@echo "==> gofumpt..."
+	@gofumpt -l -w internal/ cmd/
+	@echo "==> goimports..."
+	@goimports -w internal/ cmd/
+
+# === 格式检查（CI 用，只读不改） ===
+fmt-check:
+	@echo "==> gofumpt check..."
+	@test -z "$$(gofumpt -l internal/ cmd/)" || (echo "gofumpt: 以下文件格式不正确：" && gofumpt -l internal/ cmd/ && exit 1)
+	@echo "==> goimports check..."
+	@test -z "$$(goimports -l internal/ cmd/)" || (echo "goimports: 以下文件 import 不规范：" && goimports -l internal/ cmd/ && exit 1)
+
+# === 静态分析（报告模式，不阻断） ===
+lint:
+	@echo "==> golangci-lint (report only)..."
+	@golangci-lint run ./... || true
+
+# === 静态分析（阻断模式，CI 用） ===
+lint-strict:
+	@echo "==> golangci-lint (strict)..."
+	@golangci-lint run ./...
+
+# === 测试 ===
+test:
+	@echo "==> go test..."
+	@go test -v -race ./...
+
+# === CI 完整流程（报告模式） ===
+ci:
+	@$(MAKE) fmt-check
+	@$(MAKE) lint