快照 11 丢了，快照 12 还能解码吗：增量状态必须引用已确认基线

public readonly record struct EntityState(int X, int Health);
public readonly record struct Snapshot(long Sequence, EntityState State);
public readonly record struct SnapshotDelta(
    long Sequence, long BaselineSequence, int DeltaX, int DeltaHealth);

public sealed class SnapshotBaselineStore
{
    private readonly SortedDictionary<long, Snapshot> _sent = [];
    public Snapshot Acknowledged { get; private set; }

    public SnapshotBaselineStore(Snapshot initial) => Acknowledged = initial;

    public SnapshotDelta Encode(Snapshot current)
    {
        if (current.Sequence <= Acknowledged.Sequence || _sent.ContainsKey(current.Sequence))
            throw new ArgumentOutOfRangeException(nameof(current));

        _sent.Add(current.Sequence, current);
        return new SnapshotDelta(
            current.Sequence,
            Acknowledged.Sequence,
            current.State.X - Acknowledged.State.X,
            current.State.Health - Acknowledged.State.Health);
    }

    public bool TryAcknowledge(long sequence)
    {
        if (sequence <= Acknowledged.Sequence || !_sent.TryGetValue(sequence, out var snapshot))
            return false;

        Acknowledged = snapshot;
        foreach (var obsolete in _sent.Keys.Where(key => key <= sequence).ToArray())
            _sent.Remove(obsolete);
        return true;
    }
}

public static class SnapshotDecoder
{
    public static Snapshot Decode(Snapshot baseline, SnapshotDelta delta)
    {
        if (baseline.Sequence != delta.BaselineSequence)
            throw new InvalidOperationException("baseline mismatch");

        return new Snapshot(delta.Sequence, new EntityState(
            baseline.State.X + delta.DeltaX,
            baseline.State.Health + delta.DeltaHealth));
    }
}

var store = new SnapshotBaselineStore(new(10, new(100, 80)));
var lost = store.Encode(new(11, new(106, 75)));
var delivered = store.Encode(new(12, new(111, 70)));
var decoded = SnapshotDecoder.Decode(store.Acknowledged, delivered);

Equal(10L, lost.BaselineSequence);
Equal(10L, delivered.BaselineSequence);
Equal(new EntityState(111, 70), decoded.State);

$ dotnet build $WORK_DIR/.tmp/daily-labs/2026-08-14-1930/SnapshotBaselineProbe.csproj -c Release
Build succeeded.
    0 Warning(s)
    0 Error(s)
Time Elapsed 00:00:07.32

$ dotnet run --project $WORK_DIR/.tmp/daily-labs/2026-08-14-1930/SnapshotBaselineProbe.csproj -c Release --no-build
loss: ack=10 lost=11 delivered=12 baseline=10 delta=(11,-10) decoded=(111,70)
ack: ack=11 next=12 baseline=11 delta=(5,-5)
mismatch: clientBaseline=9 packetBaseline=10 result=rejected
tests: passed=4 failed=0 skipped=0 elapsedMs=57.6102