Settings Feature Enhancement

Nucleic-Session: 89BFAB13-D559-43FC-BE28-0B2639BECF0F
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/RemoteStore.swift

@@ -765,6 +765,44 @@ final class RemoteStore: ObservableObject {
         send(.fetchDiff(sessionID))
     }
 
+    // MARK: - Add a device to this mesh (relayed pairing-code mint)
+
+    /// Whether the "add a device" button should appear: a live Mac that advertises
+    /// `canMintPairingCode` is reachable to mint a join code (or we're in demo).
+    var canAddDeviceToMesh: Bool {
+        demoMode || pairingMintConnection != nil
+    }
+
+    /// The connection we route a mint request to: prefer the context host if it can mint, else any
+    /// live host that can. A code minted by *any* mesh member joins the whole group (mesh "join").
+    private var pairingMintConnection: HostConnection? {
+        if let ctx = contextConnection, ctx.connectivity.isLive, ctx.capabilities.canMintPairingCode {
+            return ctx
+        }
+        return connections.values.first { $0.connectivity.isLive && $0.capabilities.canMintPairingCode }
+    }
+
+    /// Ask a connected Mac to open a pairing window and hand back its join code. The reply arrives
+    /// asynchronously as `AddDeviceState.ready` (or `.unavailable`) via the host connection.
+    func requestPairingCode() {
+        if demoMode { addDevice = .ready(Self.demoPairingCode); return }
+        guard let conn = pairingMintConnection else { addDevice = .unavailable; return }
+        pairingMintHostID = conn.hostID
+        addDevice = .requesting
+        conn.send(.requestPairingCode)
+    }
+
+    /// The user dismissed the "add a device" sheet — tell the minting Mac to close its pairing
+    /// window (retire the one-time secret) and reset to idle.
+    func cancelPairingCode() {
+        if !demoMode, let id = pairingMintHostID { connections[id]?.send(.cancelPairingCode) }
+        pairingMintHostID = nil
+        addDevice = .idle
+    }
+
+    /// A stand-in join code for the offline demo so the QR/copy sheet renders without a Mac.
+    private static let demoPairingCode = "nucleic://pair?d=demo"
+
     /// Record that the user looked at this session now (clears its unseen-completion wash).
     func markOpened(_ sessionID: SessionID) {
         lastOpenedAt[sessionID] = Date()