fix(lsp): use Mason package name for Lua language server

mason-tool-installer expects the Mason registry name "lua-language-server",
not the LSP config name "lua_ls". The lsp.config/lsp.enable calls
correctly keep using "lua_ls".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

init.lua

@@ -614,7 +614,7 @@ require('lazy').setup({
       -- You can press `g?` for help in this menu.
       local ensure_installed = vim.tbl_keys(servers or {})
       vim.list_extend(ensure_installed, {
-        'lua_ls', -- Lua Language server
+        'lua-language-server', -- Lua Language server (Mason package name)
         'stylua', -- Used to format Lua code
         -- You can add other tools here that you want Mason to install
       })