Resolve Server-044..050: KillWorker accounting + admin service hardening

Server-044  KillWorkerAsync catch path now calls _metrics.SessionRemoved
            so the open-session gauge does not leak when KillWorker throws.
Server-045  KillWorkerAsync routes through a new
            GatewaySession.KillWorkerWithCloseGateAsync that takes the
            per-session close lock, so concurrent kills count SessionsClosed
            exactly once.
Server-046  CloseSessionCoreAsync's SessionCloseStartedException branch and
            ShutdownAsync's kill fallback both increment SessionsClosed (not
            just the gauge), so the counter and gauge stay consistent.
Server-047  ApiKeysPage.ConfirmPendingAsync holds PendingAction across the
            awaited action and clears it in finally, matching the sessions
            pages.
Server-048  Closed: the 044/045 regression tests cover the previously-
            untested kill paths.
Server-049  IDashboardSessionAdminService + DashboardSessionAdminService
            now carry XML docs that pin the Admin gate, missing-session
            return-Fail semantics, and the dashboard-admin-kill reason.
Server-050  CloseSessionAsync and KillWorkerAsync catch unexpected
            exceptions after the SessionManagerException catches and return
            a friendly Fail; OperationCanceledException tied to the caller
            token still propagates.

All resolved at 2026-05-24; 503/503 gateway tests pass.

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

src/ZB.MOM.WW.MxGateway.Server/Dashboard/Components/Pages/ApiKeysPage.razor

@@ -328,9 +328,18 @@ else
             return;
         }
 
+        // Server-047: align the pending-action lifecycle with SessionsPage / SessionDetailsPage —
+        // hold PendingAction while the awaited action runs so the shared ConfirmDialog can render
+        // its in-flight (IsBusy) state, then clear in finally regardless of outcome.
         Func<System.Security.Claims.ClaimsPrincipal, Task<DashboardApiKeyManagementResult>> action = PendingAction.Action;
-        PendingAction = null;
-        await RunManagementActionAsync(action).ConfigureAwait(false);
+        try
+        {
+            await RunManagementActionAsync(action).ConfigureAwait(false);
+        }
+        finally
+        {
+            PendingAction = null;
+        }
     }
 
     private sealed record PendingConfirm(