Fix BLE identity state races

bitchatTests/Services/BLELocalIdentityStateStoreTests.swift

@@ -0,0 +1,57 @@
+import BitFoundation
+import Foundation
+import Testing
+@testable import bitchat
+
+struct BLELocalIdentityStateStoreTests {
+    @Test
+    func identityReplacementUpdatesWireBytesAtomically() throws {
+        let initial = PeerID(str: "0011223344556677")
+        let replacement = PeerID(str: "8899aabbccddeeff")
+        let store = BLELocalIdentityStateStore(peerID: initial, nickname: "alice")
+
+        store.replacePeerIdentity(with: replacement)
+
+        let snapshot = store.snapshot()
+        #expect(snapshot.peerID == replacement)
+        #expect(snapshot.peerIDData == Data(hexString: replacement.id))
+        #expect(snapshot.nickname == "alice")
+    }
+
+    @Test
+    func concurrentReadsNeverObserveSplitIdentityState() {
+        let peerIDs = [
+            PeerID(str: "0011223344556677"),
+            PeerID(str: "8899aabbccddeeff")
+        ]
+        let store = BLELocalIdentityStateStore(peerID: peerIDs[0], nickname: "alice")
+        let failures = LockedFailureRecorder()
+
+        DispatchQueue.concurrentPerform(iterations: 2_000) { index in
+            if index.isMultiple(of: 2) {
+                store.replacePeerIdentity(with: peerIDs[index % peerIDs.count])
+            } else {
+                store.setNickname(index.isMultiple(of: 3) ? "alice" : "bob")
+            }
+
+            let snapshot = store.snapshot()
+            let expectedWireID = Data(hexString: snapshot.peerID.id) ?? Data()
+            if snapshot.peerIDData != expectedWireID {
+                failures.record()
+            }
+        }
+
+        #expect(!failures.hasFailure)
+    }
+}
+
+private final class LockedFailureRecorder: @unchecked Sendable {
+    private let lock = NSLock()
+    private var failed = false
+
+    var hasFailure: Bool { lock.withLock { failed } }
+
+    func record() {
+        lock.withLock { failed = true }
+    }
+}