Wipe-and-resignup left the client stuck with the blank V_new's id in
Certification.ViewerId. /tool/signup is anonymous, so it can't see the
Steam ticket and creates a fresh anonymous viewer keyed on the new UDID;
the Steam handler on the next request resolves to V_old and serves its
data, but no normal-response hook overwrites Certification.ViewerId.
GameStart now compares the UDID-keyed viewer to the auth-resolved one
and emits rewrite_viewer_id when they differ, which Cute/GameStartCheckTask
writes back into Certification.ViewerId.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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