Adds an `ExtGlob` word part with `op` and a raw `pattern` string (alternations and nested groups stay unparsed inside the pattern). Implementation lives in tokenizer/scan-extglob.ts and is invoked from the word loop before `(` is treated as a word terminator. The negation operator at a statement boundary now defers to the extended-glob scanner when followed by `(`, matching Bash semantics. Tests cover all five operators, alternation, nested parens, position tracking, and confirm a bare `?` stays a literal.