chore(make): 增强 clean 目标清理 Go 缓存

添加 go clean -cache -testcache 清理构建缓存，
注释保留 go clean -modcache 供需要时启用。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Makefile

@@ -269,6 +269,8 @@ clean:
 	@echo "Cleaning build artifacts..."
 	rm -rf $(BUILD_DIR)
 	rm -f coverage.out coverage.html
+	go clean -cache -testcache
+	# go clean -modcache
 	@echo "Clean complete."
 
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