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/shift.rs

@@ -16,7 +16,8 @@ pub fn shift(node: Node, job: &mut JobBldr) -> ShResult<()> {
     unreachable!()
   };
 
-  let (argv, _) = setup_builtin(argv, job, None)?;
+  let (argv, _) = setup_builtin(Some(argv), job, None)?;
+  let argv = argv.unwrap();
   let mut argv = argv.into_iter();
 
   if let Some((arg, span)) = argv.next() {