/ai_*_rank_battle/start now reads ViewerRankProgress for the target format
and populates SelfInfo.rank / battlePoint / isMasterRank / masterPoint so
the pre-battle screen matches the viewer's real state. Read-only path uses
IRankProgressService.GetAsync (added in this commit).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>