Closes 4 more arena-colosseum spec shapes (6/16 → 10/16): the dual-prefix
battle URLs (colosseum_battle/* and colosseum_rank_battle/*) for both
do_matching and per-match finish, plus the bracket-end /finish + /retire
pair on /arena_colosseum.
* ColosseumProgressionService: pure-logic decisions for win-threshold
advancement, 3008 promotion trigger, and per-round reward bundles.
Extends ColosseumRoundsConfig with FinishRewards/RetireRewards per
round + a top-level ChampionRewards list.
* MatchContextBuilder.BuildForColosseumAsync: lifts the registered deck
via IDeckRepository (NOT viewer-graph) per project_ef_nav_include_pitfall.
* ArenaColosseumBattleController: dual route prefixes off one controller
via explicit absolute [HttpPost("/...")] routes — does NOT extend
SVSimController's [Route("[controller]")]. Same pattern as FreeBattle.
URL-vs-IsRankMatching mismatch returns 400 with a phase-mismatch error;
no-deck triggers the standard 3001 matchmaking-illegal state. 3008
flips run.IsRankMatching exactly once via the progression service.
* /arena_colosseum/finish + /retire share FinishResponse (rewards +
reward_list + colosseum_status). Champion finish appends ChampionRewards
and surfaces colosseum_status.is_champion = true. Both delete the run
row after granting via IInventoryTransaction.GrantAsync.
* DI: ModePolicy entries for "colosseum_battle" and "colosseum_rank_battle".
* Tests: 8 progression-service unit tests (pure logic), 5 battle-controller
HTTP tests, 5 bracket-terminate HTTP tests, 2 full-bracket E2E walks
(champion path + retire mid-round). Full suite: 1331/1331.
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