Remove dead code found by full Periphery audit; add scan config + advisory CI (#1410)

Periphery 3.7.4 audit of both schemes (macOS + iOS, intersected so
platform-specific code is never touched), with test targets indexed and
the share extension built. 277 dead declarations removed or demoted:
dead forwarding wrappers (ChatViewModel+Nostr/+PrivateChat), removed-
feature remnants (autocomplete command suggestions, back-swipe tuning,
MediaSendError, GeohashParticipantTracker), unused Tor dormancy
bindings, assign-only properties, unused parameters (renamed to _), and
redundant public accessibility. 13 orphaned localization keys deleted
across all 29 locales (old pre-#1392 location-notes UI, app_info
warnings).

Two real tests were flagged as unused because they never ran: Swift
Testing methods missing @Test (NostrProtocolTests.
testAckRoundTripNIP44V2_Delivered, NotificationStreamAssemblerTests.
testAssemblesCompressedLargeFrame). Re-armed both; they pass.

Deliberately kept, now recorded in .periphery.baseline.json: iOS-only
code invisible to the CI macOS scan, C FFI signatures, keep-alive
NWPathMonitor reference, InboundEventKey.eventID (dedup semantics),
wifiBulk capability bit (reserved for Wi-Fi bulk work, used by
BitFoundation package tests), and the String secureClear cluster
(exercised by package tests).

New: .periphery.yml config and an advisory Dead Code CI job (mirrors
the SwiftLint precedent from #1361) that fails on findings not in the
committed baseline.

Verified: full macOS app suite, BitFoundation (119) and BitLogger (13)
package tests green; periphery scan --strict exits clean.

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchat/Nostr/NostrIdentity.swift

@@ -6,14 +6,12 @@ struct NostrIdentity: Codable {
     let privateKey: Data
     let publicKey: Data
     let npub: String // Bech32-encoded public key
-    let createdAt: Date
-    
+
     /// Memberwise initializer
-    init(privateKey: Data, publicKey: Data, npub: String, createdAt: Date) {
+    init(privateKey: Data, publicKey: Data, npub: String, createdAt _: Date) {
         self.privateKey = privateKey
         self.publicKey = publicKey
         self.npub = npub
-        self.createdAt = createdAt
     }
     
     /// Generate a new Nostr identity
@@ -39,12 +37,6 @@ struct NostrIdentity: Codable {
         self.privateKey = privateKeyData
         self.publicKey = xOnlyPubkey
         self.npub = try Bech32.encode(hrp: "npub", data: xOnlyPubkey)
-        self.createdAt = Date()
-    }
-    
-    /// Get signing key for event signatures
-    func signingKey() throws -> P256K.Signing.PrivateKey {
-        try P256K.Signing.PrivateKey(dataRepresentation: privateKey)
     }
     
     /// Get Schnorr signing key for Nostr event signatures

bitchat/Nostr/NostrIdentityBridge.swift

@@ -37,14 +37,6 @@ final class NostrIdentityBridge {
         return nostrIdentity
     }
     
-    /// Associate a Nostr identity with a Noise public key (for favorites)
-    func associateNostrIdentity(_ nostrPubkey: String, with noisePublicKey: Data) {
-        let key = "nostr-noise-\(noisePublicKey.base64EncodedString())"
-        if let data = nostrPubkey.data(using: .utf8) {
-            keychain.save(key: key, data: data, service: keychainService, accessible: nil)
-        }
-    }
-    
     /// Get Nostr public key associated with a Noise public key
     func getNostrPublicKey(for noisePublicKey: Data) -> String? {
         let key = "nostr-noise-\(noisePublicKey.base64EncodedString())"

bitchat/Nostr/NostrProtocol.swift

@@ -548,37 +548,6 @@ struct NostrProtocol {
         return sharedSecretData
     }
     
-    // Direct version that doesn't try to add prefixes
-    private static func deriveSharedSecretDirect(
-        privateKey: P256K.Schnorr.PrivateKey,
-        publicKey: Data
-    ) throws -> Data {
-        // Direct shared secret calculation
-        
-        // Convert Schnorr private key to KeyAgreement private key
-        let keyAgreementPrivateKey = try P256K.KeyAgreement.PrivateKey(
-            dataRepresentation: privateKey.dataRepresentation
-        )
-        
-        // Use the public key as-is (should already have prefix)
-        let keyAgreementPublicKey = try P256K.KeyAgreement.PublicKey(
-            dataRepresentation: publicKey,
-            format: .compressed
-        )
-        
-        // Perform ECDH
-        let sharedSecret = try keyAgreementPrivateKey.sharedSecretFromKeyAgreement(
-            with: keyAgreementPublicKey,
-            format: .compressed
-        )
-        
-        // Convert SharedSecret to Data
-        let sharedSecretData = sharedSecret.withUnsafeBytes { Data($0) }
-        
-        // Return raw ECDH shared secret; HKDF is applied by deriveNIP44V2Key
-        return sharedSecretData
-    }
-    
     private static func randomizedTimestamp() -> Date {
         // Add random offset to current time for privacy
         // This prevents timing correlation attacks while the actual message timestamp
@@ -708,11 +677,8 @@ struct NostrEvent: Codable {
 
 enum NostrError: Error {
     case invalidPublicKey
-    case invalidPrivateKey
     case invalidEvent
     case invalidCiphertext
-    case signingFailed
-    case encryptionFailed
 }
 
 // MARK: - NIP-44 v2 helpers (XChaCha20-Poly1305)

bitchat/Nostr/NostrRelayManager.swift

@@ -117,7 +117,6 @@ final class NostrRelayManager: ObservableObject {
         let url: String
         var isConnected: Bool = false
         var lastError: Error?
-        var lastConnectedAt: Date?
         var messagesSent: Int = 0
         var messagesReceived: Int = 0
         var reconnectAttempts: Int = 0
@@ -347,7 +346,6 @@ final class NostrRelayManager: ObservableObject {
             relays[index].nextReconnectTime = nil
             if resetState {
                 relays[index].lastError = nil
-                relays[index].lastConnectedAt = nil
                 relays[index].lastDisconnectedAt = nil
                 relays[index].messagesSent = 0
                 relays[index].messagesReceived = 0
@@ -1075,7 +1073,6 @@ final class NostrRelayManager: ObservableObject {
             relays[index].isConnected = isConnected
             relays[index].lastError = error
             if isConnected {
-                relays[index].lastConnectedAt = dependencies.now()
                 relays[index].reconnectAttempts = 0  // Reset on successful connection
                 relays[index].nextReconnectTime = nil
             } else {