AiStartInternal builds the self MatchContext, picks a bot from
IBotRoster, projects to the AiBattleStartResponseDto with camelCase
wire keys (sleeveId, emblemId, ... — see ai-start.md). turnState=0
(player first) is the safe default per the ai-start.md TODO; live
capture would clarify the enum.
No deck → ai_id=-1 fallback (the documented "no AI assigned" sentinel
per AIBattleStartTask.cs:21). 3 new wire-shape tests assert the
camelCase keys land verbatim in the JSON, plus self/oppo info come from
the right sources.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>