feat(arena-colosseum): playable bracket + rank-match promotion (phase 2)

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.

SVSim.EmulatedEntrypoint/Services/ArenaColosseum/ColosseumProgressionService.cs

@@ -0,0 +1,69 @@
+using SVSim.Database.Models;
+using SVSim.Database.Models.Config;
+
+namespace SVSim.EmulatedEntrypoint.Services.ArenaColosseum;
+
+public class ColosseumProgressionService : IColosseumProgressionService
+{
+    /// <summary>Colosseum-specific node signal — see do-matching.md §matching_state 3008.</summary>
+    public const int PromoteToRankMatchingState = 3008;
+
+    public bool ShouldPromoteToRankMatching(ViewerArenaColosseumRun run, int matchingState) =>
+        matchingState == PromoteToRankMatchingState && !run.IsRankMatching;
+
+    public AdvancementDecision DecideAdvancement(ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds)
+    {
+        var currentRound = rounds.Rounds.FirstOrDefault(r => r.RoundId == run.RoundId);
+        var currentGroup = currentRound?.Groups.FirstOrDefault();
+        var maxRoundId = rounds.Rounds.Count == 0 ? run.RoundId : rounds.Rounds.Max(r => r.RoundId);
+
+        // No matching round config (e.g. content not seeded) — treat current state as terminal
+        // so the controller doesn't loop forever. Champion=false because we can't tell.
+        if (currentGroup is null)
+        {
+            return new AdvancementDecision(run.RoundId, IsBracketEnd: true, IsChampion: false);
+        }
+
+        // Cleared the breakthrough threshold this round.
+        if (run.WinCount >= currentGroup.BreakthroughNumber)
+        {
+            bool isFinal = run.RoundId >= maxRoundId;
+            return new AdvancementDecision(
+                NextRoundId: isFinal ? run.RoundId : run.RoundId + 1,
+                IsBracketEnd: isFinal,
+                IsChampion: isFinal);
+        }
+
+        // Exhausted the per-round battle cap without clearing — bracket ends at current round.
+        if (run.BattleCountThisRound >= currentGroup.MaxBattleCount)
+        {
+            return new AdvancementDecision(run.RoundId, IsBracketEnd: true, IsChampion: false);
+        }
+
+        // Mid-round, still playing.
+        return new AdvancementDecision(run.RoundId, IsBracketEnd: false, IsChampion: false);
+    }
+
+    public IReadOnlyList<ColosseumRoundsConfig.RewardEntry> BuildRetireRewards(
+        ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds)
+    {
+        var round = rounds.Rounds.FirstOrDefault(r => r.RoundId == run.RoundId);
+        return round?.RetireRewards ?? new();
+    }
+
+    public IReadOnlyList<ColosseumRoundsConfig.RewardEntry> BuildFinishRewards(
+        ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds)
+    {
+        var round = rounds.Rounds.FirstOrDefault(r => r.RoundId == run.RoundId);
+        var bundle = new List<ColosseumRoundsConfig.RewardEntry>();
+        if (round is not null)
+        {
+            bundle.AddRange(round.FinishRewards);
+        }
+        if (run.IsChampion)
+        {
+            bundle.AddRange(rounds.ChampionRewards);
+        }
+        return bundle;
+    }
+}

SVSim.EmulatedEntrypoint/Services/ArenaColosseum/IColosseumProgressionService.cs

@@ -0,0 +1,39 @@
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.Database.Models.Config;
+
+namespace SVSim.EmulatedEntrypoint.Services.ArenaColosseum;
+
+/// <summary>
+/// Pure-logic decisions for the Colosseum bracket lifecycle. Reads a
+/// <see cref="ViewerArenaColosseumRun"/> + <see cref="ColosseumRoundsConfig"/> snapshot and
+/// returns advancement / promotion / reward decisions. Side-effectful (debits, grants,
+/// run-row writes) live on the controllers — this service just computes.
+/// </summary>
+public interface IColosseumProgressionService
+{
+    /// <summary>True when the node signal <c>matching_state == 3008</c> indicates the run
+    /// has been promoted to the ranked bracket and we haven't already flipped the flag.
+    /// Subsequent battle URLs route to <c>colosseum_rank_battle/*</c>.</summary>
+    bool ShouldPromoteToRankMatching(ViewerArenaColosseumRun run, int matchingState);
+
+    /// <summary>Triggered post-match-finish when wins/losses cross thresholds. Returns the
+    /// next round id (or current if no change), whether the bracket has ended, and the
+    /// champion flag for the final-round-cleared case.</summary>
+    AdvancementDecision DecideAdvancement(ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds);
+
+    /// <summary>Bundle to grant on <c>/retire</c>. Reads
+    /// <see cref="ColosseumRoundsConfig.RoundEntry.RetireRewards"/> for the run's
+    /// <see cref="ViewerArenaColosseumRun.RoundId"/>. Empty when no matching round.</summary>
+    IReadOnlyList<ColosseumRoundsConfig.RewardEntry> BuildRetireRewards(
+        ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds);
+
+    /// <summary>Bundle to grant on <c>/finish</c>. Combines the current round's
+    /// <see cref="ColosseumRoundsConfig.RoundEntry.FinishRewards"/> with
+    /// <see cref="ColosseumRoundsConfig.ChampionRewards"/> when the run is a champion.</summary>
+    IReadOnlyList<ColosseumRoundsConfig.RewardEntry> BuildFinishRewards(
+        ViewerArenaColosseumRun run, ColosseumRoundsConfig rounds);
+}
+
+/// <summary>Output of <see cref="IColosseumProgressionService.DecideAdvancement"/>.</summary>
+public sealed record AdvancementDecision(int NextRoundId, bool IsBracketEnd, bool IsChampion);