Merge remote-tracking branch 'origin/feat/mesh-diagnostics' into feat/integration-all

# Conflicts:
#	bitchat/Models/CommandInfo.swift
#	bitchat/Services/BLE/BLEOutboundPacketPolicy.swift
#	bitchat/Services/BLE/BLEReceivePipeline.swift
#	bitchat/Services/BLE/BLEService.swift
#	bitchat/Services/CommandProcessor.swift
#	bitchat/Services/Transport.swift
#	bitchat/Sync/SyncTypeFlags.swift
#	bitchat/ViewModels/ChatViewModel.swift
#	bitchatTests/BLEServiceCoreTests.swift
#	localPackages/BitFoundation/Sources/BitFoundation/MessageType.swift

localPackages/BitFoundation/Sources/BitFoundation/MeshPingPayload.swift

@@ -0,0 +1,57 @@
+//
+// MeshPingPayload.swift
+// BitFoundation
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import struct Foundation.Data
+
+/// Wire payload shared by the `ping` (0x26) and `pong` (0x27) message types.
+///
+/// Layout (9 bytes):
+/// - 8 bytes: random nonce (a pong echoes the nonce of the ping it answers)
+/// - 1 byte: origin TTL — the TTL the packet was launched with, so the
+///   receiver can compute the hop count as `originTTL - receivedTTL`.
+///
+/// Both directions are unencrypted and unsigned: the payload carries no
+/// private data, and the unguessable nonce already binds a pong to a probe
+/// the local device actually sent.
+public struct MeshPingPayload: Equatable {
+    public static let nonceLength = 8
+    private static let encodedLength = nonceLength + 1
+
+    public let nonce: Data
+    public let originTTL: UInt8
+
+    public init?(nonce: Data, originTTL: UInt8) {
+        guard nonce.count == Self.nonceLength else { return nil }
+        self.nonce = nonce
+        self.originTTL = originTTL
+    }
+
+    public func encode() -> Data {
+        var data = Data(capacity: Self.encodedLength)
+        data.append(nonce)
+        data.append(originTTL)
+        return data
+    }
+
+    /// Accepts payloads with trailing bytes so future revisions can extend
+    /// the format without breaking older clients.
+    public static func decode(_ data: Data) -> MeshPingPayload? {
+        guard data.count >= encodedLength else { return nil }
+        let nonce = Data(data.prefix(nonceLength))
+        let originTTL = data[data.index(data.startIndex, offsetBy: nonceLength)]
+        return MeshPingPayload(nonce: nonce, originTTL: originTTL)
+    }
+
+    /// Number of links a packet crossed, derived from TTL decrements plus the
+    /// final delivery link (a directly connected peer is 1 hop away).
+    /// Returns nil when the TTLs are inconsistent (received above origin).
+    public static func hopCount(originTTL: UInt8, receivedTTL: UInt8) -> Int? {
+        guard originTTL >= receivedTTL else { return nil }
+        return Int(originTTL - receivedTTL) + 1
+    }
+}

localPackages/BitFoundation/Sources/BitFoundation/MessageType.swift

@@ -25,14 +25,18 @@ public enum MessageType: UInt8 {
     case fragment = 0x20        // Single fragment type for large messages
     case fileTransfer = 0x22    // Binary file/audio/image payloads
 
-    // 0x23/0x26/0x27 reserved by other in-flight features.
+    // 0x23 reserved by other in-flight features.
     case prekeyBundle = 0x24    // Signed batch of one-time prekeys (gossiped)
     case groupMessage = 0x25    // Group-encrypted broadcast (cleartext group ID, ChaChaPoly body)
+    // Mesh diagnostics
+    case ping = 0x26            // Directed echo request (nonce + origin TTL)
+    case pong = 0x27            // Directed echo reply (echoed nonce + origin TTL)
     // Gateway mode: signed Nostr event ferried between a mesh-only peer and
     // an internet gateway peer.
     case nostrCarrier = 0x28
 
 
+
     public var description: String {
         switch self {
         case .announce: return "announce"
@@ -46,6 +50,8 @@ public enum MessageType: UInt8 {
         case .fileTransfer: return "fileTransfer"
         case .prekeyBundle: return "prekeyBundle"
         case .groupMessage: return "groupMessage"
+        case .ping: return "ping"
+        case .pong: return "pong"
         case .nostrCarrier: return "nostrCarrier"
         }
     }