The router's own isIn check answered a mode it did not know with
express-validator's "Invalid value" before titles.validateSettings could
say which words are allowed. Found on the walk; the router now checks shape
only, as every other phase-17 route does.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY