feat: add devtools (tree-sitter, neovim, formatter, CLI commands)

- Add tree-sitter grammar for syntax highlighting
- Add Neovim plugin with syntax, LSP integration, and commands
- Add code formatter (lux fmt) with check mode
- Add CLI commands: fmt, check, test, watch, init
- Add project initialization with lux.toml template

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

editors/nvim/ftplugin/lux.vim

@@ -0,0 +1,29 @@
+" Lux filetype settings
+
+" Indentation
+setlocal expandtab
+setlocal shiftwidth=4
+setlocal softtabstop=4
+setlocal tabstop=4
+
+" Comments
+setlocal commentstring=//\ %s
+setlocal comments=://
+
+" Folding
+setlocal foldmethod=syntax
+
+" Match pairs
+setlocal matchpairs+=<:>
+
+" Format options
+setlocal formatoptions-=t
+setlocal formatoptions+=croql
+
+" Completion
+setlocal omnifunc=v:lua.vim.lsp.omnifunc
+
+" Key mappings for Lux development
+nnoremap <buffer> <localleader>r :!lux %<CR>
+nnoremap <buffer> <localleader>f :!lux fmt %<CR>
+nnoremap <buffer> <localleader>t :!lux test<CR>