♻️ 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_semantic/test_semantic.cppm

@@ -436,7 +436,7 @@ namespace
     }
 }
 
-int main(int argc, char** argv)
+export int Run(int argc, char** argv)
 {
     try
     {