The 22-case TokenType mapping was split across three initializers to
stay under the complexity lint, leaving a preconditionFailure default
the types could not prove unreachable, which also tripped the
forbidden-patterns gate on every push. One exhaustive switch makes a
new TokenType case a compile error instead of a runtime trap; the lint
now ignores case statements when counting complexity, since exhaustive
closed-enum switches are the point, not a smell.
