♻️ refactor(lsp_server): move entrypoints out of named modules

- export Run() from launcher module and add non-module main TU
- apply same pattern to module-based test executables
- migrate utils/string implementation fully into string.cppm and drop string.cpp
- point clangd to linux build compilation database

lsp-server/test/test_module/CMakeLists.txt

@@ -12,7 +12,7 @@ endif()
 
 set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
 
-add_executable(test_module main.cppm)
+add_executable(test_module main.cppm main.cc)
 target_sources(
   test_module
   PRIVATE

lsp-server/test/test_module/main.cc

@@ -0,0 +1,6 @@
+import lsp.test.module_demo.main;
+
+int main()
+{
+    return Run();
+}

lsp-server/test/test_module/main.cppm

@@ -7,7 +7,7 @@ import std;
 import math;
 import math2;
 
-int main()
+export int Run()
 {
     std::cout << "hello std module\n";
     std::vector<int> v{ 1, 2, 3 };