fix: add disconnect detection + drop inter-command delay to 50ms

Two changes:
1. DXSmartProvisioner now registers for BLE disconnect callbacks.
   Previously if the beacon dropped the link mid-write, the provisioner
   would sit waiting for ACK timeouts (5s × 2 retries = 10s of dead air).
   Now it fails immediately with a clear error.

2. Inter-command delay reduced from 150ms → 50ms since beacon handles
   fast writes fine.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

PayfritBeacon/Provisioners/DXSmartProvisioner.swift

@@ -41,6 +41,7 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
     private(set) var isConnected = false
     private(set) var isFlashing = false  // Beacon LED flashing after trigger
     private var useNewSDK = true         // Prefer new SDK, fallback to old
+    private var disconnected = false     // Set true when BLE link drops unexpectedly
     var diagnosticLog: ProvisionLog?
     var bleManager: BLEManager?
 
@@ -76,6 +77,14 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
                 await diagnosticLog?.log("auth", "Authenticating (trigger + password)…")
                 try await authenticate()
                 await diagnosticLog?.log("auth", "Auth complete — SDK: \(useNewSDK ? "new (FFE2)" : "old (FFE1)")")
+
+                // Register for unexpected disconnects so we fail fast instead of
+                // waiting for per-command ACK timeouts (5s × 2 = 10s of dead air).
+                bleManager?.onPeripheralDisconnected = { [weak self] disconnectedPeripheral, error in
+                    guard disconnectedPeripheral.identifier == self?.peripheral.identifier else { return }
+                    self?.handleUnexpectedDisconnect(error: error)
+                }
+
                 isConnected = true
                 isFlashing = true
                 return
@@ -125,6 +134,8 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
     }
 
     func disconnect() {
+        // Unregister disconnect handler so intentional disconnect doesn't trigger error path
+        bleManager?.onPeripheralDisconnected = nil
         if peripheral.state == .connected || peripheral.state == .connecting {
             centralManager.cancelPeripheralConnection(peripheral)
         }
@@ -171,6 +182,12 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
         ]
 
         for (index, (name, packet)) in commands.enumerated() {
+            // Bail immediately if BLE link dropped between commands
+            if disconnected {
+                await diagnosticLog?.log("write", "Aborting — BLE disconnected", isError: true)
+                throw ProvisionError.writeFailed("BLE disconnected during write sequence")
+            }
+
             await diagnosticLog?.log("write", "[\(index + 1)/\(commands.count)] \(name) (\(packet.count) bytes)")
 
             // SaveConfig (last command) causes beacon MCU to reboot — it never sends an ACK.
@@ -205,8 +222,8 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
                 throw lastError
             }
 
-            // 150ms between commands — aggressive speedup (was 300ms, originally 500ms)
-            try await Task.sleep(nanoseconds: 150_000_000)
+            // 50ms between commands — beacon handles fast writes fine (was 150ms, 300ms, 500ms)
+            try await Task.sleep(nanoseconds: 50_000_000)
         }
     }
 
@@ -282,6 +299,32 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
         return packet
     }
 
+    // MARK: - Disconnect Detection
+
+    /// Called when BLE link drops unexpectedly during provisioning.
+    /// Immediately resolves any pending continuations so we fail fast
+    /// instead of waiting for the 5s operationTimeout.
+    private func handleUnexpectedDisconnect(error: Error?) {
+        disconnected = true
+        isConnected = false
+        let disconnectError = ProvisionError.writeFailed("BLE disconnected unexpectedly: \(error?.localizedDescription ?? "unknown")")
+        Task { await diagnosticLog?.log("ble", "⚠️ Unexpected disconnect during provisioning", isError: true) }
+
+        // Cancel any pending write/response continuation immediately
+        if let cont = responseContinuation {
+            responseContinuation = nil
+            cont.resume(throwing: disconnectError)
+        }
+        if let cont = writeContinuation {
+            writeContinuation = nil
+            cont.resume(throwing: disconnectError)
+        }
+        if let cont = connectionContinuation {
+            connectionContinuation = nil
+            cont.resume(throwing: disconnectError)
+        }
+    }
+
     // MARK: - Private Helpers
 
     private func connectOnce() async throws {