♻️ 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/CMakeLists.txt

@@ -17,9 +17,9 @@ endif()
 set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
 
 set(SOURCES
+    main.cc
     test_semantic.cppm
     ../../src/utils/string.cppm
-    ../../src/utils/string.cpp
     ../../src/language/symbol/internal/builder.cppm
     ../../src/language/symbol/internal/store.cppm
     ../../src/language/symbol/internal/table.cppm