feat(central-ui): FlowDebugService relays Retry/Discard for a parked outbound step

Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29

src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/IFlowDebugService.cs

@@ -23,6 +23,16 @@ public sealed record FlowDebugOutcome(FlowGraph? Graph, FlowDebugRunResult? Raw,
     public static FlowDebugOutcome Fail(string error, string errorCode) => new(null, null, error, errorCode);
 }
 
+/// <summary>
+/// Outcome of a Retry / Discard relayed from a Flow Debugger node (follow-ups plan 2026-09-06 D4).
+/// <see cref="Message"/> is operator-facing and uses the same wording as the Site Calls /
+/// Notification report pages, whether the relay was refused before it left the page or the
+/// owning site / outbox answered.
+/// </summary>
+/// <param name="Success">True when the relay was applied (site <c>Applied</c>, or outbox success).</param>
+/// <param name="Message">What happened, in the report pages' words.</param>
+public sealed record FlowOutboundActionResult(bool Success, string Message);
+
 /// <summary>
 /// CentralUI facade over the Flow Debugger (design 2026-09-05 §5.5/§7.1): static shape
 /// prediction from script syntax, and the three management commands (Live run of a method,
@@ -66,4 +76,24 @@ public interface IFlowDebugService
     /// <param name="executionId">Any execution id in the chain.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
     Task<FlowDebugOutcome> ReplayAsync(Guid executionId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Relays a Retry of a parked outbound node to its owner — the Site Call Audit relay for an
+    /// <see cref="FlowStepKind.ApiCall"/> / <see cref="FlowStepKind.DbCall"/> (keyed by the step's
+    /// <see cref="FlowStep.CorrelationId"/> = <c>TrackedOperationId</c> and <see cref="FlowStep.SiteId"/>),
+    /// the Notification Outbox for a <see cref="FlowStepKind.Notify"/> (<c>CorrelationId</c> =
+    /// <c>NotificationId</c>). A step that is not outbound, not <see cref="FlowStepOutcome.Parked"/>,
+    /// has no correlation id, or (site kinds) no site id is refused with a message and never relayed.
+    /// </summary>
+    /// <param name="step">The outbound step to retry.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task<FlowOutboundActionResult> RetryOutboundAsync(FlowStep step, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Relays a Discard of a parked outbound node to its owner. Same routing and refusals as
+    /// <see cref="RetryOutboundAsync"/>.
+    /// </summary>
+    /// <param name="step">The outbound step to discard.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task<FlowOutboundActionResult> DiscardOutboundAsync(FlowStep step, CancellationToken cancellationToken = default);
 }