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.

tests/lsp_plugin_test.cpp

@@ -0,0 +1,153 @@
+// ============================================================================
+// lsp_plugin_test.cpp — LSP 插件单元测试 (轻量 CHECK 宏，离线环境无 GoogleTest)
+// ============================================================================
+// 测试 LSP 插件的可独立验证功能:
+//   - lsp_trim: 字符串 trim 逻辑
+//   - lsp_frame_message: Content-Length header 构建
+//   - lsp_parse_content_length: Content-Length header 解析
+// ============================================================================
+
+#include "lsp_internal.hpp"
+
+#include "dstalk/dstalk_host.h"
+
+#include <cstdarg>
+#include <cstring>
+#include <iostream>
+#include <string>
+
+static int g_failures = 0;
+
+// Lightweight assertion macros (matches project pattern used by other tests)
+#define CHECK(cond, msg) do {                                  \
+    if (!(cond)) {                                             \
+        std::cerr << "[FAIL] " << (msg) << "\n";               \
+        ++g_failures;                                          \
+    }                                                          \
+} while (0)
+
+#define CHECK_EQ(actual, expected, msg) do {                   \
+    auto _a = (actual);                                        \
+    auto _e = (expected);                                      \
+    if (!(_a == _e)) {                                         \
+        std::cerr << "[FAIL] " << (msg)                        \
+                  << " (got=" << _a << " expected=" << _e << ")\n"; \
+        ++g_failures;                                          \
+    }                                                          \
+} while (0)
+
+// ----------------------------------------------------------------------------
+// lsp_trim
+// ----------------------------------------------------------------------------
+static void test_lsp_trim() {
+    CHECK_EQ(lsp_trim(""), std::string(""), "trim empty string");
+    CHECK_EQ(lsp_trim("hello"), std::string("hello"), "trim no whitespace");
+    CHECK_EQ(lsp_trim("   hello"), std::string("hello"), "trim leading spaces");
+    CHECK_EQ(lsp_trim("hello   "), std::string("hello"), "trim trailing spaces");
+    CHECK_EQ(lsp_trim("  hello  "), std::string("hello"), "trim both sides");
+    CHECK_EQ(lsp_trim("\t\n\rhello\t\n\r"), std::string("hello"), "trim tabs/newlines");
+    CHECK_EQ(lsp_trim("   \t\n\r  "), std::string(""), "trim only whitespace");
+    CHECK_EQ(lsp_trim("A"), std::string("A"), "trim single char");
+    CHECK_EQ(lsp_trim("  hello world  "), std::string("hello world"),
+             "trim preserves internal whitespace");
+}
+
+// ----------------------------------------------------------------------------
+// lsp_frame_message
+// ----------------------------------------------------------------------------
+static void test_lsp_frame_message() {
+    {
+        std::string frame = lsp_frame_message("");
+        CHECK(frame.find("Content-Length: 0") != std::string::npos,
+              "frame empty body has Content-Length: 0");
+        CHECK(frame.find("\r\n\r\n") != std::string::npos,
+              "frame empty body has header separator");
+        CHECK(frame.find("\r\n\r\n") + 4 == frame.size(),
+              "frame empty body ends right after separator");
+    }
+    {
+        std::string body = "{\"jsonrpc\":\"2.0\"}";
+        std::string frame = lsp_frame_message(body);
+        CHECK(frame.find("Content-Length: " + std::to_string(body.size())) != std::string::npos,
+              "frame simple body Content-Length matches");
+        CHECK(frame.find(body) != std::string::npos, "frame simple body present");
+    }
+    {
+        std::string body = "line1\nline2\nline3";
+        std::string frame = lsp_frame_message(body);
+        CHECK(frame.find("Content-Length: " + std::to_string(body.size())) != std::string::npos,
+              "frame multiline body Content-Length matches");
+        CHECK(frame.find(body) != std::string::npos, "frame multiline body present");
+    }
+    {
+        std::string body(std::string("\x00\x01\x02\x03\xFF", 5));
+        std::string frame = lsp_frame_message(body);
+        CHECK(frame.find("Content-Length: 5") != std::string::npos,
+              "frame binary body Content-Length: 5");
+    }
+}
+
+// ----------------------------------------------------------------------------
+// lsp_parse_content_length
+// ----------------------------------------------------------------------------
+static void test_lsp_parse_content_length() {
+    CHECK_EQ(lsp_parse_content_length("Content-Length: 1234"), 1234, "parse valid header");
+    CHECK_EQ(lsp_parse_content_length("  Content-Length: 42"), 42, "parse leading spaces");
+    CHECK_EQ(lsp_parse_content_length("content-length: 99"), 99, "parse lowercase");
+    CHECK_EQ(lsp_parse_content_length("CONTENT-LENGTH: 77"), 77, "parse uppercase");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: 0"), 0, "parse zero length");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: 1048576"), 1048576, "parse large value");
+    CHECK_EQ(lsp_parse_content_length(""), -1, "parse empty string");
+    CHECK_EQ(lsp_parse_content_length("Content-Lengthh: 10"), -1, "parse misspelled (extra h)");
+    CHECK_EQ(lsp_parse_content_length("ContentLength: 10"), -1, "parse misspelled (no hyphen)");
+    CHECK_EQ(lsp_parse_content_length("Content-Length 10"), -1, "parse missing colon");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: abc"), -1, "parse non-numeric");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: -5"), -5, "parse negative");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: 999999999999"), -1, "parse overflow");
+    CHECK_EQ(lsp_parse_content_length(std::string("\x00\x01\xFF", 3)), -1, "parse garbage input");
+    CHECK_EQ(lsp_parse_content_length("Content-Length: 1234abc"), 1234, "parse trailing garbage");
+    CHECK_EQ(lsp_parse_content_length("Content-Type: application/vscode-jsonrpc"), -1,
+             "parse other LSP header returns -1");
+}
+
+// ----------------------------------------------------------------------------
+// frame + parse round-trip
+// ----------------------------------------------------------------------------
+static void test_round_trip() {
+    {
+        std::string body = "{\"jsonrpc\":\"2.0\",\"method\":\"initialize\"}";
+        std::string frame = lsp_frame_message(body);
+        size_t header_end = frame.find("\r\n\r\n");
+        CHECK(header_end != std::string::npos, "round-trip simple finds header end");
+        if (header_end != std::string::npos) {
+            std::string header_block = frame.substr(0, header_end);
+            CHECK_EQ(lsp_parse_content_length(header_block), static_cast<int>(body.size()),
+                     "round-trip simple Content-Length matches body size");
+        }
+    }
+    {
+        std::string body;
+        std::string frame = lsp_frame_message(body);
+        size_t header_end = frame.find("\r\n\r\n");
+        CHECK(header_end != std::string::npos, "round-trip empty finds header end");
+        if (header_end != std::string::npos) {
+            std::string header_block = frame.substr(0, header_end);
+            CHECK_EQ(lsp_parse_content_length(header_block), 0,
+                     "round-trip empty Content-Length is 0");
+        }
+    }
+}
+
+int main() {
+    test_lsp_trim();
+    test_lsp_frame_message();
+    test_lsp_parse_content_length();
+    test_round_trip();
+
+    if (g_failures == 0) {
+        std::cout << "lsp_plugin_test: all checks passed\n";
+        return 0;
+    }
+    std::cerr << "lsp_plugin_test: " << g_failures << " check(s) failed\n";
+    return 1;
+}