feat(anomaly): suspension-freeze detector

- Add SuspensionFreezeDetector via the IAnomalyDetector seam: a suspension gap with
  the favourite unchanged and a negligible (< threshold) price move — the mirror of
  the flip. Score = how completely the line froze. Reuses MatchWinEvidence so UI +
  evaluator handle it unchanged. 6 tests.
- Add AnomalyKind.SuspensionFreeze + localized card/detail label, SuspensionFreezeThreshold
  option, and fan it into DetectAnomaliesUseCase.

src/Marathon.Application/Configuration/AnomalyOptions.cs

@@ -44,4 +44,11 @@ public sealed class AnomalyOptions
     /// to flag a steam move. Must be in (0, 1). Default: 0.20 (20 percentage points).
     /// </summary>
     public decimal SteamMoveDriftThreshold { get; init; } = 0.20m;
+
+    /// <summary>
+    /// Maximum normalised implied-probability change across a suspension for it to count
+    /// as a "freeze" (line resumed essentially unchanged). Must be in (0, 1).
+    /// Default: 0.05 (5 percentage points).
+    /// </summary>
+    public decimal SuspensionFreezeThreshold { get; init; } = 0.05m;
 }

src/Marathon.Application/UseCases/DetectAnomaliesUseCase.cs

@@ -70,6 +70,10 @@ public sealed class DetectAnomaliesUseCase
                 _options.SteamMoveDriftThreshold,
                 _options.MinSnapshotCount,
                 _options.SuspensionGapSeconds),
+            new SuspensionFreezeDetector(
+                _options.SuspensionGapSeconds,
+                _options.SuspensionFreezeThreshold,
+                _options.MinSnapshotCount),
         };
 
         var events = await _eventRepo.ListAsync(ct);

src/Marathon.Domain/AnomalyDetection/SuspensionFreezeDetector.cs

@@ -0,0 +1,107 @@
+using Marathon.Domain.Entities;
+using Marathon.Domain.Enums;
+using Marathon.Domain.ValueObjects;
+
+namespace Marathon.Domain.AnomalyDetection;
+
+/// <summary>
+/// Detects a "suspension freeze": the market was suspended (a gap larger than
+/// <c>suspensionGapSeconds</c> between adjacent live snapshots) but resumed with
+/// essentially the same line — the favourite is unchanged and the largest normalised
+/// implied-probability move is below <c>freezeThreshold</c>.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This is the mirror image of <see cref="AnomalyDetector"/> (SuspensionFlip): the flip
+/// fires on a large favourite-changing move across a suspension; the freeze fires when
+/// the bookmaker paused but did <i>not</i> move — a tell that they were uncertain or
+/// gathering information rather than repricing.
+/// </para>
+/// <para>
+/// Score = how completely the line froze: <c>1 − (maxMove / freezeThreshold)</c>, so a
+/// perfectly unchanged line scores ~1.0 and one near the threshold scores near 0. The
+/// shared <see cref="MatchWinEvidence"/> shape (pre ≈ post) conveys the freeze directly,
+/// and the outcome evaluator grades the unchanged favourite like any other anomaly.
+/// </para>
+/// </remarks>
+public sealed class SuspensionFreezeDetector : IAnomalyDetector
+{
+    private readonly int _suspensionGapSeconds;
+    private readonly decimal _freezeThreshold;
+    private readonly int _minSnapshotCount;
+
+    /// <param name="suspensionGapSeconds">Minimum adjacent-snapshot gap (seconds) classed as a suspension.</param>
+    /// <param name="freezeThreshold">Maximum normalised probability move to count as frozen; in (0, 1).</param>
+    /// <param name="minSnapshotCount">Minimum live snapshots before detection runs (>= 2).</param>
+    public SuspensionFreezeDetector(int suspensionGapSeconds, decimal freezeThreshold, int minSnapshotCount)
+    {
+        if (suspensionGapSeconds <= 0)
+            throw new ArgumentOutOfRangeException(nameof(suspensionGapSeconds), suspensionGapSeconds, "Must be positive.");
+        if (freezeThreshold is <= 0m or >= 1m)
+            throw new ArgumentOutOfRangeException(nameof(freezeThreshold), freezeThreshold, "Must be in (0, 1).");
+        if (minSnapshotCount < 2)
+            throw new ArgumentOutOfRangeException(nameof(minSnapshotCount), minSnapshotCount, "Must be at least 2.");
+
+        _suspensionGapSeconds = suspensionGapSeconds;
+        _freezeThreshold = freezeThreshold;
+        _minSnapshotCount = minSnapshotCount;
+    }
+
+    /// <inheritdoc />
+    public IReadOnlyList<Anomaly> Detect(EventId eventId, IReadOnlyList<OddsSnapshot> snapshots)
+    {
+        ArgumentNullException.ThrowIfNull(eventId);
+        ArgumentNullException.ThrowIfNull(snapshots);
+
+        var live = snapshots
+            .Where(s => s.Source == OddsSource.Live)
+            .OrderBy(s => s.CapturedAt)
+            .ToList();
+
+        if (live.Count < _minSnapshotCount)
+            return Array.Empty<Anomaly>();
+
+        var suspensionGap = TimeSpan.FromSeconds(_suspensionGapSeconds);
+        var anomalies = new List<Anomaly>();
+
+        for (int i = 0; i < live.Count - 1; i++)
+        {
+            var pre = live[i];
+            var post = live[i + 1];
+            if (post.CapturedAt - pre.CapturedAt <= suspensionGap)
+                continue;
+
+            var preProbs = MatchWinEvidence.Extract(pre);
+            var postProbs = MatchWinEvidence.Extract(post);
+            if (preProbs is null || postProbs is null)
+                continue;
+
+            decimal maxMove = Math.Max(
+                Math.Abs(postProbs.P1 - preProbs.P1),
+                Math.Abs(postProbs.P2 - preProbs.P2));
+            if (preProbs.PDraw.HasValue && postProbs.PDraw.HasValue)
+                maxMove = Math.Max(maxMove, Math.Abs(postProbs.PDraw.Value - preProbs.PDraw.Value));
+
+            var favouriteUnchanged =
+                MatchWinEvidence.Favourite(preProbs) == MatchWinEvidence.Favourite(postProbs);
+
+            // Strictly below the threshold so the score stays in (0, 1].
+            if (!favouriteUnchanged || maxMove >= _freezeThreshold)
+                continue;
+
+            var score = 1m - (maxMove / _freezeThreshold);
+            var gapSeconds = (int)(post.CapturedAt - pre.CapturedAt).TotalSeconds;
+            var evidenceJson = MatchWinEvidence.BuildJson(gapSeconds, pre, preProbs, post, postProbs);
+
+            anomalies.Add(new Anomaly(
+                Id:          Guid.NewGuid(),
+                EventId:     eventId,
+                DetectedAt:  MoscowTime.Now,
+                Kind:        AnomalyKind.SuspensionFreeze,
+                Score:       score,
+                EvidenceJson: evidenceJson));
+        }
+
+        return anomalies.AsReadOnly();
+    }
+}

src/Marathon.Domain/Enums/AnomalyKind.cs

@@ -16,4 +16,10 @@ public enum AnomalyKind
     /// continuous window (no suspension) — money moving the line ("steam").
     /// </summary>
     SteamMove,
+
+    /// <summary>
+    /// The bookmaker suspended the market but resumed with essentially the same line
+    /// (favourite unchanged, negligible price move) — a freeze signalling uncertainty.
+    /// </summary>
+    SuspensionFreeze,
 }

src/Marathon.Hosts.WpfBlazor/appsettings.json

@@ -43,7 +43,8 @@
     "MinSnapshotCount": 3,
     "DetectionIntervalSeconds": 60,
     "SteamMoveWindowSeconds": 120,
-    "SteamMoveDriftThreshold": 0.20
+    "SteamMoveDriftThreshold": 0.20,
+    "SuspensionFreezeThreshold": 0.05
   },
   "Notifications": {
     "Enabled": false,

src/Marathon.UI/Components/AnomalyCard.razor

@@ -211,9 +211,10 @@
 
     private string KindLabel(AnomalyKind kind) => kind switch
     {
-        AnomalyKind.SuspensionFlip => L["Anomaly.Kind.SuspensionFlip"],
+        AnomalyKind.SuspensionFlip   => L["Anomaly.Kind.SuspensionFlip"],
-        AnomalyKind.SteamMove      => L["Anomaly.Kind.SteamMove"],
+        AnomalyKind.SteamMove        => L["Anomaly.Kind.SteamMove"],
-        _                          => kind.ToString(),
+        AnomalyKind.SuspensionFreeze => L["Anomaly.Kind.SuspensionFreeze"],
+        _                            => kind.ToString(),
     };
 
     private string SportLabel(int code) => SportLabels.Resolve(L, code);

src/Marathon.UI/Pages/Anomalies/Detail.razor

@@ -105,9 +105,10 @@
 
     private string KindLabel(AnomalyKind kind) => kind switch
     {
-        AnomalyKind.SuspensionFlip => L["Anomaly.Kind.SuspensionFlip"],
+        AnomalyKind.SuspensionFlip   => L["Anomaly.Kind.SuspensionFlip"],
-        AnomalyKind.SteamMove      => L["Anomaly.Kind.SteamMove"],
+        AnomalyKind.SteamMove        => L["Anomaly.Kind.SteamMove"],
-        _                          => kind.ToString(),
+        AnomalyKind.SuspensionFreeze => L["Anomaly.Kind.SuspensionFreeze"],
+        _                            => kind.ToString(),
     };
 
     private static string FormatGap(int seconds)

src/Marathon.UI/Resources/SharedResource.en.resx

@@ -167,6 +167,7 @@
   <data name="Anomaly.Live"><value>Anomaly</value></data>
   <data name="Anomaly.Kind.SuspensionFlip"><value>Suspension flip</value></data>
   <data name="Anomaly.Kind.SteamMove"><value>Steam move</value></data>
+  <data name="Anomaly.Kind.SuspensionFreeze"><value>Suspension freeze</value></data>
   <data name="Anomaly.Score"><value>Confidence</value></data>
 
   <!-- Phase 7 — Anomaly feed UI -->

src/Marathon.UI/Resources/SharedResource.ru.resx

@@ -180,6 +180,7 @@
   <data name="Anomaly.Live"><value>Аномалия</value></data>
   <data name="Anomaly.Kind.SuspensionFlip"><value>Разворот после заморозки</value></data>
   <data name="Anomaly.Kind.SteamMove"><value>Движение линии</value></data>
+  <data name="Anomaly.Kind.SuspensionFreeze"><value>Заморозка линии</value></data>
   <data name="Anomaly.Score"><value>Уверенность</value></data>
 
   <!-- Phase 7 — Лента аномалий -->

tests/Marathon.Domain.Tests/AnomalyDetection/SuspensionFreezeDetectorTests.cs

@@ -0,0 +1,104 @@
+using FluentAssertions;
+using Marathon.Domain.AnomalyDetection;
+using Marathon.Domain.Entities;
+using Marathon.Domain.Enums;
+using Marathon.Domain.ValueObjects;
+
+namespace Marathon.Domain.Tests.AnomalyDetection;
+
+public sealed class SuspensionFreezeDetectorTests
+{
+    private static readonly TimeSpan MoscowOffset = TimeSpan.FromHours(3);
+    private static readonly DateTimeOffset BaseTime = new(2026, 5, 10, 18, 0, 0, MoscowOffset);
+    private static readonly EventId Event = new("26000002");
+
+    // suspension gap 60s, freeze threshold 0.05, min 3 snapshots.
+    private static SuspensionFreezeDetector CreateSut() => new(60, 0.05m, 3);
+
+    private static OddsSnapshot Live(int seconds, decimal r1, decimal r2) =>
+        new(Event, BaseTime.AddSeconds(seconds), OddsSource.Live,
+            new List<Bet>
+            {
+                new(MatchScope.Instance, BetType.Win, Side.Side1, null, new OddsRate(r1)),
+                new(MatchScope.Instance, BetType.Win, Side.Side2, null, new OddsRate(r2)),
+            });
+
+    [Fact]
+    public void Should_FlagFreeze_When_SuspensionResumesUnchanged()
+    {
+        // 90s gap between the 2nd and 3rd snapshot; line resumes identical.
+        var snapshots = new[]
+        {
+            Live(0,   1.5m, 3.0m),
+            Live(30,  1.5m, 3.0m),
+            Live(120, 1.5m, 3.0m), // 90s gap, unchanged
+            Live(150, 1.5m, 3.0m),
+        };
+
+        var result = CreateSut().Detect(Event, snapshots);
+
+        result.Should().ContainSingle();
+        result[0].Kind.Should().Be(AnomalyKind.SuspensionFreeze);
+        result[0].Score.Should().Be(1.0m, "an unchanged line is a complete freeze");
+    }
+
+    [Fact]
+    public void Should_NotFlag_When_FlipAcrossSuspension()
+    {
+        // Favourite changes across the gap — that is the SuspensionFlip detector's job.
+        var snapshots = new[]
+        {
+            Live(0,   1.3m, 4.0m),
+            Live(30,  1.3m, 4.0m),
+            Live(120, 4.0m, 1.3m), // 90s gap, flipped
+            Live(150, 4.0m, 1.3m),
+        };
+
+        CreateSut().Detect(Event, snapshots).Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Should_NotFlag_When_NoSuspensionGap()
+    {
+        // Continuous 30s steps — no gap exceeds the 60s suspension threshold.
+        var snapshots = new[]
+        {
+            Live(0,  1.5m, 3.0m),
+            Live(30, 1.5m, 3.0m),
+            Live(60, 1.5m, 3.0m),
+        };
+
+        CreateSut().Detect(Event, snapshots).Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Should_ReturnEmpty_When_FewerThanMinSnapshots()
+    {
+        var snapshots = new[] { Live(0, 1.5m, 3.0m), Live(120, 1.5m, 3.0m) };
+
+        CreateSut().Detect(Event, snapshots).Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Should_EmitParseableEvidence_For_DetectedFreeze()
+    {
+        var snapshots = new[]
+        {
+            Live(0,   1.5m, 3.0m),
+            Live(30,  1.5m, 3.0m),
+            Live(120, 1.5m, 3.0m),
+        };
+
+        var anomaly = CreateSut().Detect(Event, snapshots).First();
+
+        AnomalyEvidenceParser.TryParse(anomaly.EvidenceJson, out var data).Should().BeTrue();
+        data.PreSuspension.Favourite.Should().Be(data.PostSuspension.Favourite, "the favourite is unchanged in a freeze");
+    }
+
+    [Fact]
+    public void Should_Throw_When_FreezeThresholdOutOfRange()
+    {
+        var act = () => new SuspensionFreezeDetector(60, 0m, 3);
+        act.Should().Throw<ArgumentOutOfRangeException>();
+    }
+}