Add array support for local/export/readonly builtins

Add array length syntax ${arr[#]}

Map read path now expands variables before splitting on ., fixing map "$node" with dotted paths

Map assignment path uses quote-aware token splitting, enabling quoted keys like "--type="

Completion errors now display above prompt instead of being overwritten

Fix nested if/fi parser bug when closing keywords appear on separate lines

Add QuoteState enum, replacing ad-hoc quote tracking booleans across lexer, highlighter, and expansion

Add split_tk_at/split_tk for quote-aware token splitting with span preservation

Refactor setup_builtin to accept optional argv for deferred expansion

Add ariadne dependency (not yet wired up)

src/builtin/echo.rs

@@ -51,7 +51,8 @@ pub fn echo(node: Node, io_stack: &mut IoStack, job: &mut JobBldr) -> ShResult<(
   assert!(!argv.is_empty());
   let (argv, opts) = get_opts_from_tokens(argv, &ECHO_OPTS)?;
   let flags = get_echo_flags(opts).blame(blame)?;
-  let (argv, _guard) = setup_builtin(argv, job, Some((io_stack, node.redirs)))?;
+  let (argv, _guard) = setup_builtin(Some(argv), job, Some((io_stack, node.redirs)))?;
+  let argv = argv.unwrap();
 
   let output_channel = if flags.contains(EchoFlags::USE_STDERR) {
     borrow_fd(STDERR_FILENO)