Add capability bits to announce TLV (#1375)

Announces now carry an optional capabilities TLV (0x05): a little-endian
bitfield with named bits for upcoming features (prekeys, wifiBulk,
gateway, groups, board, vouch, meshDiagnostics). Old clients skip the
unknown TLV; peers without it decode as nil so features can distinguish
"legacy peer" from "advertises nothing".

PeerCapabilities lives in BitFoundation with a minimal-length encoding
that preserves unknown bits for forward compatibility. Peer capabilities
are stored in the BLE peer registry on verified announce and exposed via
BLEService.peerCapabilities(_:). The local advertisement set is empty
until each feature ships its bit.

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

bitchat/Services/BLE/BLEPeerRegistry.swift

@@ -9,6 +9,7 @@ struct BLEPeerInfo: Equatable {
     var signingPublicKey: Data?
     var isVerifiedNickname: Bool
     var lastSeen: Date
+    var capabilities: PeerCapabilities = []
 }
 
 struct BLEPeerAnnounceUpdate: Equatable {
@@ -107,6 +108,10 @@ struct BLEPeerRegistry {
         peers[peerID]?.noisePublicKey?.sha256Fingerprint()
     }
 
+    func capabilities(for peerID: PeerID) -> PeerCapabilities {
+        peers[peerID.toShort()]?.capabilities ?? []
+    }
+
     func displayNicknames(selfNickname: String) -> [PeerID: String] {
         let connected = peers.filter { $0.value.isConnected }
         let tuples = connected.map { ($0.key, $0.value.nickname, true) }
@@ -157,7 +162,8 @@ struct BLEPeerRegistry {
         noisePublicKey: Data,
         signingPublicKey: Data?,
         isConnected: Bool,
-        now: Date
+        now: Date,
+        capabilities: PeerCapabilities = []
     ) -> BLEPeerAnnounceUpdate {
         let existing = peers[peerID]
         let update = BLEPeerAnnounceUpdate(
@@ -173,7 +179,8 @@ struct BLEPeerRegistry {
             noisePublicKey: noisePublicKey,
             signingPublicKey: signingPublicKey,
             isVerifiedNickname: true,
-            lastSeen: now
+            lastSeen: now,
+            capabilities: capabilities
         )
 
         return update

bitchat/Services/BLE/BLEService.swift

@@ -619,6 +619,12 @@ final class BLEService: NSObject {
         }
     }
 
+    /// Capabilities the peer advertised in its last verified announce.
+    /// Empty for peers that predate the capabilities TLV.
+    func peerCapabilities(_ peerID: PeerID) -> PeerCapabilities {
+        collectionsQueue.sync { peerRegistry.capabilities(for: peerID) }
+    }
+
     func getPeerNicknames() -> [PeerID: String] {
         return collectionsQueue.sync {
             peerRegistry.displayNicknames(selfNickname: myNickname)
@@ -1261,7 +1267,8 @@ final class BLEService: NSObject {
             nickname: myNickname,
             noisePublicKey: noisePub,
             signingPublicKey: signingPub,
-            directNeighbors: connectedPeerIDs
+            directNeighbors: connectedPeerIDs,
+            capabilities: PeerCapabilities.localSupported
         )
         
         guard let payload = announcement.encode() else {
@@ -3315,7 +3322,8 @@ extension BLEService {
                     noisePublicKey: announcement.noisePublicKey,
                     signingPublicKey: announcement.signingPublicKey,
                     isConnected: isConnected,
-                    now: now
+                    now: now,
+                    capabilities: announcement.capabilities ?? []
                 ) ?? BLEPeerAnnounceUpdate(isNewPeer: false, wasDisconnected: false, previousNickname: nil)
             },
             shouldEmitReconnectLog: { [weak self] peerID, now in