feat: add first-class Neovim support with enhanced formatting

- Add modern Lua implementation with modular architecture
- Implement HEREDOC preservation and smart comment indentation
- Create dual implementation (Neovim Lua + VimScript fallback)
- Add comprehensive health check and configuration system
- Enhance formatting engine with state machine for context awareness
- Update documentation with Lua configuration examples
- Add memory files for development workflow and conventions

lua/shellspec/config.lua

@@ -0,0 +1,51 @@
+-- ShellSpec configuration management
+local M = {}
+
+-- Default configuration
+M.defaults = {
+  -- Auto-format on save
+  auto_format = false,
+
+  -- Indentation settings
+  indent_size = 2,
+  use_spaces = true,
+
+  -- HEREDOC handling
+  heredoc_patterns = {
+    "<<[A-Z_][A-Z0-9_]*", -- <<EOF, <<DATA, etc.
+    "<<'[^']*'", -- <<'EOF'
+    '<<"[^"]*"', -- <<"EOF"
+    "<<-[A-Z_][A-Z0-9_]*", -- <<-EOF (with leading tab removal)
+  },
+
+  -- Comment indentation
+  indent_comments = true,
+
+  -- Formatting options
+  preserve_empty_lines = true,
+  max_line_length = 160,
+}
+
+-- Current configuration
+M.config = {}
+
+-- Setup function
+function M.setup(opts)
+  M.config = vim.tbl_deep_extend("force", M.defaults, opts or {})
+
+  -- Validate configuration
+  if type(M.config.indent_size) ~= "number" or M.config.indent_size < 1 then
+    vim.notify("shellspec: indent_size must be a positive number", vim.log.levels.WARN)
+    M.config.indent_size = M.defaults.indent_size
+  end
+end
+
+-- Get configuration value
+function M.get(key)
+  return M.config[key]
+end
+
+-- Initialize with defaults
+M.setup()
+
+return M