Add hunting-tournament.md covering the 公式狩猟大会 system: game
context (cups, schedule, rewards), what is already implemented in
develop (handlers_tournament.go is mostly functional), and the four
remaining gaps requiring RE — quest clear time recording, ClanID
leaderboard filtering, AcquireTournament reward delivery, and guild
cup soul attribution to Mezeporta Festival.
Documents why feature/hunting-tournament is not mergeable (duplicate
handlers) and preserves its useful findings: ClanID field name on
EnumerateOrder and the festa timing corrections.
Update unimplemented.md open branches summary accordingly.
