feat: Add LSP plugin unit tests and frontend common initialization library

- Introduced `dstalk_lsp_plugin_test` for testing LSP plugin functionalities including `lsp_trim`, `lsp_frame_message`, and `lsp_parse_content_length`.
- Created `dstalk_frontend_common` static library to encapsulate shared initialization logic for frontend components (CLI, GUI, Web).
- Implemented configuration file discovery and service querying in `dstalk_frontend_init`.
- Added internal headers for LSP and Anthropic plugins to facilitate unit testing.
- Established a mailroom system for asynchronous message passing between stateless agents, enhancing coordination and context management.

plugins_upper/anthropic/src/anthropic_internal.hpp

@@ -0,0 +1,46 @@
+// ============================================================================
+// anthropic_internal.hpp — 内部声明：供单元测试访问的函数与数据结构
+// ============================================================================
+// 仅在 tests 中使用；非 plugin 公共 API
+// ============================================================================
+
+#ifndef ANTHROPIC_INTERNAL_HPP
+#define ANTHROPIC_INTERNAL_HPP
+
+#include "dstalk/dstalk_host.h"
+#include "dstalk/dstalk_services.h"
+
+#include "ai_common.hpp"
+
+#include <string>
+#include <vector>
+
+// ---- 从 dstalk_ai 命名空间导入共享类型与函数 ----
+using dstalk_ai::PluginConfig;
+using dstalk_ai::ToolCallAccum;
+using dstalk_ai::StreamContext;
+using dstalk_ai::secure_zero;
+using dstalk_ai::extract_host_port;
+
+// ---- 全局变量 ----
+extern PluginConfig g_cfg;
+extern std::string g_tools_json;
+
+// ---- 测试用函数声明 ----
+bool parse_sse_data(const std::string& data, std::string& token_out,
+                    StreamContext* ctx);
+
+std::string build_request_json(const dstalk_message_t* history, int history_len,
+                               const std::string& user_input,
+                               const std::string& tools_json,
+                               bool stream);
+
+std::string build_headers_json();
+
+void my_free_result(dstalk_chat_result_t* result);
+
+int my_configure(const char* provider, const char* base_url,
+                 const char* api_key, const char* model,
+                 int max_tokens, double temperature);
+
+#endif // ANTHROPIC_INTERNAL_HPP