Desktop: keep a vault-visibility failure from closing the app, and leave a crash log when anything else does

src/DodoSSH.Client.Session/ClientPaths.cs

@@ -122,6 +122,9 @@ public sealed record ClientPaths(string DataDirectory)
     /// </remarks>
     public string InstanceLockFile => Path.Combine(DataDirectory, "instance.lock");
 
+    /// <summary>Where the application writes down why it died, when something nothing caught ends it.</summary>
+    public string CrashLogFile => Path.Combine(DataDirectory, "crash.log");
+
     /// <summary>Creates the profile directory if it is not there yet.</summary>
     /// <remarks>
     /// Separate from resolving the path, because resolving must never have a side effect: it is read