Remove unused IScheduleRestart interface and its dead registration plumbing (#165)

The IScheduleRestart interface existed only to be stored in
FlowsManager._scheduleRestarts, a write-only dictionary that fed the
immediate in-process restart of an idle target - a path already disabled
as a stopgap. Since it was populated but never read, remove it entirely:

- Delete IScheduleRestart.cs
- Drop the interface from Invoker (and its explicit-impl adapter)
- Remove _scheduleRestarts and RegisterScheduleRestart from FlowsManager,
  trimming the stopgap remarks that documented the dead plumbing
- Remove the three RegisterScheduleRestart calls in FunctionsRegistry

Schedule() still delivers via the durable interrupt + PostponedWatchdog,
so behaviour is unchanged.

Author: stidsborg

Core/Cleipnir.ResilientFunctions/CoreRuntime/FlowsManager.cs

@@ -10,7 +10,6 @@ namespace Cleipnir.ResilientFunctions.CoreRuntime;
 public class FlowsManager : IFlowsManager
 {
     private readonly Dictionary<StoredId, FlowState> _dict = new();
-    private readonly Dictionary<StoredType, IScheduleRestart> _scheduleRestarts = new();
     private readonly IFunctionStore _functionStore;
     private readonly Lock _lock = new();
 
@@ -54,27 +53,12 @@ public Task Push(IReadOnlyDictionary<StoredId, List<StoredMessage>> messagesByFl
         return Task.WhenAll(tasks);
     }
 
-    public void RegisterScheduleRestart(StoredType storedType, IScheduleRestart scheduleRestart)
-    {
-        lock (_lock)
-            _scheduleRestarts[storedType] = scheduleRestart;
-    }
-
     /// <summary>
     /// Wakes the target flow so it consumes the just-published message by applying the durable interrupt
     /// (interrupted flag + expires=0) - the suspend-race guard and watchdog backstop, so the message is never
     /// lost even when the target suspends concurrently or is owned by another replica. An idle target this
     /// replica executes is then picked up by the PostponedWatchdog.
     /// </summary>
-    /// <remarks>
-    /// STOPGAP: the immediate in-process restart of an idle target - look up <see cref="_scheduleRestarts"/>
-    /// by <see cref="StoredId.Type"/> for a flow not in <c>_dict</c> and await
-    /// <see cref="IScheduleRestart.ScheduleRestart"/> - is disabled. It races with the suspend/resume
-    /// machinery and deadlocks the ping-pong / multi-flow message exchange. The durable interrupt below still
-    /// guarantees delivery via the PostponedWatchdog. Restore the immediate restart once the suspension rework
-    /// lands. <see cref="RegisterScheduleRestart"/> keeps populating <see cref="_scheduleRestarts"/> so that
-    /// re-enabling is a local change here.
-    /// </remarks>
     public Task Schedule(StoredId storedId)
         => _functionStore.Interrupt(storedId);
 }

Core/Cleipnir.ResilientFunctions/CoreRuntime/IScheduleRestart.cs

@@ -11,7 +11,7 @@
 
 namespace Cleipnir.ResilientFunctions.CoreRuntime.Invocation;
 
-public class Invoker<TParam, TReturn> : IScheduleRestart
+public class Invoker<TParam, TReturn>
 {
     private readonly FlowType _flowType;
     private readonly StoredType _storedType;
@@ -203,8 +203,6 @@ public async Task<InnerScheduled<TReturn>> ScheduleRestart(StoredId storedId)
         return _invocationHelper.CreateInnerScheduled([flowId], parentWorkflow: null, detach: null, tcs.Task);
     }
 
-    Task IScheduleRestart.ScheduleRestart(StoredId storedId) => ScheduleRestart(storedId);
-
     internal async Task ScheduleRestart(StoredId storedId, RestartedFunction rf, Action onCompletion)
     {
         var tcs = new TaskCompletionSource<TReturn>();

Core/Cleipnir.ResilientFunctions/CoreRuntime/Invocation/Invoker.cs

@@ -259,7 +259,6 @@ public FuncRegistration<TParam, TReturn> RegisterFunc<TParam, TReturn>(
                 _flowsManager
             );
 
-            _flowsManager.RegisterScheduleRestart(storedType, invoker);
             WatchDogsFactory.CreateAndStart(
                 flowType,
                 storedType,
@@ -345,7 +344,6 @@ private ParamlessRegistration RegisterParamless(
                 _flowsManager
             );
 
-            _flowsManager.RegisterScheduleRestart(storedType, invoker);
             WatchDogsFactory.CreateAndStart(
                 flowType,
                 storedType,
@@ -431,7 +429,6 @@ public ActionRegistration<TParam> RegisterAction<TParam>(
                 _flowsManager
             );
 
-            _flowsManager.RegisterScheduleRestart(storedType, rActionInvoker);            
             WatchDogsFactory.CreateAndStart(
                 flowType,
                 storedType,