Reduce test-process churn to fix flaky CI exit hang

The app test job intermittently hung at process exit. The suite is
load-sensitive and historically prone to cooperative-pool/teardown
deadlocks; the security changes added background work to the test process
that pushed it over the edge. Make the unit-test BLEService/identity
manager quiescent and remove blocking sync:

- forceSave() no longer does queue.sync(.barrier). It is reachable from
  deinit and from async tests on the swift-concurrency cooperative pool,
  where a blocking barrier-sync can starve/deadlock the pool. It now
  cancels the debounce timer and persists directly. (Removed the
  now-unneeded queue-specific-key re-entrancy machinery.)
- SecureIdentityStateManager persists synchronously under tests instead of
  scheduling a DispatchSourceTimer that lingers past process exit.
- Gate gossip-sync start (in addition to the maintenance timer) behind
  real Bluetooth init, so the test BLEService runs no periodic
  sign/broadcast/sync churn.
- Skip the panic Nostr reconnect under tests (connecting the shared relay
  singleton starts network/reconnect work that never completes).

Production behavior is unchanged: real Bluetooth builds run all timers and
the debounced save as before; the debounce save now actually fires
(previously a Timer on a GCD queue that never ran).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bitchat/ViewModels/ChatViewModel.swift

@@ -1180,19 +1180,25 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, TransportEventDele
         // No need to force UserDefaults synchronization
 
         // Reinitialize Nostr with new identity
-        // This will generate new Nostr keys derived from new Noise keys
-        Task { @MainActor in
-            // Small delay to ensure cleanup completes
-            try? await Task.sleep(nanoseconds: TransportConfig.uiAsyncShortSleepNs) // 0.1 seconds
+        // This will generate new Nostr keys derived from new Noise keys.
+        // Skipped under tests: connecting the shared relay singleton starts
+        // real network/reconnect work that never completes and would keep the
+        // test process alive (the singleton, unlike a discardable instance, is
+        // never deallocated to cancel it).
+        if !TestEnvironment.isRunningTests {
+            Task { @MainActor in
+                // Small delay to ensure cleanup completes
+                try? await Task.sleep(nanoseconds: TransportConfig.uiAsyncShortSleepNs) // 0.1 seconds
 
-            // Reinitialize Nostr relay manager with new identity. Reuse the
-            // shared singleton — every other component (NostrTransport, geohash
-            // subscriptions, AppRuntime observers) is bound to `.shared`, so
-            // creating a fresh instance here would split relay state and leave
-            // sends running against a disconnected manager.
-            nostrRelayManager = NostrRelayManager.shared
-            setupNostrMessageHandling()
-            nostrRelayManager?.connect()
+                // Reinitialize Nostr relay manager with new identity. Reuse the
+                // shared singleton — every other component (NostrTransport, geohash
+                // subscriptions, AppRuntime observers) is bound to `.shared`, so
+                // creating a fresh instance here would split relay state and leave
+                // sends running against a disconnected manager.
+                nostrRelayManager = NostrRelayManager.shared
+                setupNostrMessageHandling()
+                nostrRelayManager?.connect()
+            }
         }
 
         // Delete ALL media files (incoming and outgoing) in background