Inject notification/favorites singletons through coordinator contexts

NotificationService.shared and FavoritesPersistenceService.shared
accesses across nine coordinators/components consolidate into
ChatViewModel witnesses behind intent-named context members
(notifyPrivateMessage, notifyMention, favoriteRelationship(forNoiseKey:),
allFavoriteRelationships, postLocalNotification, ...). Singleton reach
from coordinators is now zero; nine new tests cover previously
untestable notification/favorites flows.

Also root-causes the long-flaky gift-wrap dedup test: parallel tests
share LocationChannelManager.shared, so channel-switch tests trigger
clearProcessedNostrEvents() on every live ChatViewModel, wiping the
dedup record mid-test. The invariant (forged-signature copies never
poison dedup) now lives as a deterministic NostrInboundPipeline
mock-context test; two Schnorr concurrency probes added along the way
stay as regression guards for the P256K shared-context assumptions.

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

bitchatTests/ChatPublicConversationCoordinatorContextTests.swift

@@ -7,11 +7,11 @@
 // `ChatViewModel`, following the `ChatDeliveryCoordinatorContextTests` /
 // `ChatPrivateConversationCoordinatorContextTests` exemplars.
 //
-// Scope note: flows that hit process-wide singletons are intentionally not
-// exercised here — `checkForMentions` / haptics (NotificationService.shared,
-// UIApplication) and the geohash branch of `sendPublicRaw`
-// (NostrRelayManager.shared, GeoRelayDirectory.shared). The mesh branch of
-// `sendPublicRaw` and all timeline/store/blocking flows are covered.
+// Scope note: haptics (UIApplication) and the geohash branch of
+// `sendPublicRaw` (NostrRelayManager.shared, GeoRelayDirectory.shared) are
+// intentionally not exercised here. `checkForMentions` posts through the
+// injected context (`notifyMention(from:message:)`) and is covered, as are
+// the mesh branch of `sendPublicRaw` and all timeline/store/blocking flows.
 //
 
 import Testing
@@ -249,6 +249,13 @@ private final class MockChatPublicConversationContext: ChatPublicConversationCon
         prewarmedMessageIDs.append(message.id)
     }
 
+    // Notifications
+    private(set) var mentionNotifications: [(sender: String, message: String)] = []
+
+    func notifyMention(from sender: String, message: String) {
+        mentionNotifications.append((sender, message))
+    }
+
     static let dummyIdentity = NostrIdentity(
         privateKey: Data(repeating: 0x11, count: 32),
         publicKey: Data(repeating: 0x22, count: 32),
@@ -502,4 +509,51 @@ struct ChatPublicConversationCoordinatorContextTests {
         let unknownHex = String(repeating: "12", count: 32)
         #expect(coordinator.displayNameForNostrPubkey(unknownHex) == "anon#" + unknownHex.suffix(4))
     }
+    @Test @MainActor
+    func checkForMentions_postsMentionNotificationOnlyForOthersMentioningMe() async {
+        let context = MockChatPublicConversationContext()
+        let coordinator = ChatPublicConversationCoordinator(context: context)
+
+        // A mention of my nickname from someone else notifies.
+        coordinator.checkForMentions(
+            BitchatMessage(
+                id: "mention-1",
+                sender: "alice",
+                content: "hey @me",
+                timestamp: Date(),
+                isRelay: false,
+                mentions: ["me"]
+            )
+        )
+        #expect(context.mentionNotifications.count == 1)
+        #expect(context.mentionNotifications.first?.sender == "alice")
+        #expect(context.mentionNotifications.first?.message == "hey @me")
+
+        // Mentioning someone else does not notify.
+        coordinator.checkForMentions(
+            BitchatMessage(
+                id: "mention-2",
+                sender: "alice",
+                content: "hey @bob",
+                timestamp: Date(),
+                isRelay: false,
+                mentions: ["bob"]
+            )
+        )
+        #expect(context.mentionNotifications.count == 1)
+
+        // My own message mentioning myself does not notify.
+        coordinator.checkForMentions(
+            BitchatMessage(
+                id: "mention-3",
+                sender: "me",
+                content: "talking about @me",
+                timestamp: Date(),
+                isRelay: false,
+                mentions: ["me"]
+            )
+        )
+        #expect(context.mentionNotifications.count == 1)
+    }
+
 }