fix: restore \$state on SvelteMap in device-mapping-dialog

The variable is fully reassigned in an \$effect, so \$state is required
for reactivity. Suppress the no-unnecessary-state-wrap lint rule with a
comment explaining the reason.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/play/components/device-mapping-dialog.svelte

@@ -16,7 +16,8 @@
   let { open, recordedDevices, connectedDevices, onConfirm, onCancel }: Props = $props();
 
   // Device mappings: recorded device name -> connected device
-  let mappings = new SvelteMap<string, BluetoothDevice>();
+  // eslint-disable-next-line svelte/no-unnecessary-state-wrap -- variable is reassigned in $effect, $state is required
+  let mappings = $state(new SvelteMap<string, BluetoothDevice>());
 
   // Check if a connected device is compatible with a recorded device
   function isCompatible(recordedDevice: DeviceInfo, connectedDevice: BluetoothDevice): boolean {