fix(decision-core): Hello-disabled fast-path in HandleDesktopArrivedV1 (PR2/3)

When HelloPolicyEnabled is explicitly false AND AccountSetup has been reached,
synthesise HelloOutcome="Skipped" on DesktopArrived and route directly through
Finalizing instead of waiting out the full HelloSafety 300s window. This is the
belt-and-suspenders companion to PR1's EspExiting reducer path: whichever fires
first wins, and the dual-path design survives a future regression in either
half (missing EspExiting adapter or missing HelloPolicyDetected adapter).

Both guards are required:
- HelloPolicyEnabled?.Value == false (policy explicitly disabled)
- AccountSetupEnteredUtc != null (mirrors ShouldTransitionToAwaitingHello)

This prevents a premature mid-DeviceSetup completion if HelloPolicyDetected
happens to fire before AccountSetup is observed. Unknown policy
(HelloPolicyEnabled == null) keeps the prior pessimistic behaviour.

The fast-path cancels HelloSafety on its way through so a deadline armed by an
earlier EspExiting cannot fire post-Completion and dead-end in the reducer.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Shared/AutopilotMonitor.DecisionCore/Engine/DecisionEngine.Classic.cs

@@ -243,6 +243,15 @@ namespace AutopilotMonitor.DecisionCore.Engine
         /// Handle <see cref="DecisionSignalKind.DesktopArrived"/>. Mirror of the Hello handler:
         /// records <see cref="DecisionState.DesktopArrivedUtc"/>, and if Hello has already
         /// resolved the session completes here.
+        /// <para>
+        /// Hello-disabled fast-path: when <see cref="DecisionState.HelloPolicyEnabled"/> is
+        /// explicitly <c>false</c> AND we have reached AccountSetup (so the Hello-skip is the
+        /// genuine post-ESP state rather than a premature mid-DeviceSetup classification),
+        /// synthesise <c>HelloOutcome="Skipped"</c> here and route directly through Finalizing.
+        /// This avoids waiting out the full 5-min HelloSafety window when the policy reader
+        /// already told us no Hello wizard is expected. Belt-and-suspenders alongside the
+        /// EspExiting → HelloSafety reducer path: the path that fires first wins.
+        /// </para>
         /// </summary>
         private DecisionStep HandleDesktopArrivedV1(DecisionState state, DecisionSignal signal)
         {
@@ -254,6 +263,32 @@ namespace AutopilotMonitor.DecisionCore.Engine
 
             var helloAlreadyResolved = state.HelloResolvedUtc != null;
 
+            // Hello-disabled fast-path. Both guards required:
+            //   1. HelloPolicyEnabled?.Value == false — policy reader confirmed no Hello wizard
+            //   2. AccountSetupEnteredUtc != null    — same gate as ShouldTransitionToAwaitingHello,
+            //      prevents a premature pre-AccountSetup completion if HelloPolicyDetected fires
+            //      before AccountSetup is observed.
+            // Skipping unknown policy (HelloPolicyEnabled == null) preserves the prior pessimistic
+            // behaviour: keep waiting for Hello / HelloSafety.
+            if (!helloAlreadyResolved
+                && state.HelloPolicyEnabled?.Value == false
+                && state.AccountSetupEnteredUtc != null)
+            {
+                builder.HelloResolvedUtc = new SignalFact<DateTime>(signal.OccurredAtUtc, signal.SessionSignalOrdinal);
+                builder.HelloOutcome = new SignalFact<string>("Skipped", signal.SessionSignalOrdinal);
+                // Cancel HelloSafety if it was armed by an earlier EspExiting — we're completing
+                // now via the fast-path, the deadline would otherwise fire post-Completion and
+                // dead-end in the reducer.
+                builder.CancelDeadline(DeadlineNames.HelloSafety);
+
+                return TransitionToFinalizing(
+                    state: state,
+                    signal: signal,
+                    preparedBuilder: builder,
+                    nextStepIndex: nextStep,
+                    trigger: nameof(DecisionSignalKind.DesktopArrived) + ":HelloDisabledFastPath");
+            }
+
             // Plan §5 Fix 6: mirror of HandleHelloResolvedV1. When both prerequisites are in,
             // go through Finalizing (non-terminal) instead of jumping straight to Completed.
             if (helloAlreadyResolved)