Remembered lists are global; add Clear buttons in Preferences

Remembered peers were already machine-wide for the main app; remembered apps are
now global too (a shared address book across all profiles), so it doesn't confuse
the user with a different list per profile.

- RemSoundSettingsStore.Load/SaveRememberedApplications (global, NOT written into
  profile files) mirrors remembered peers. Removed the per-profile
  Profile.RememberedSendApplications. Ticking an app in any profile adds it to the
  global list (RememberCheckedApps); the per-profile SelectedSendApplications
  (the active/ticked subset) is unchanged.
- Preferences -> General now has two buttons at the end, under a 'Remembered
  lists (shared across all profiles)' header: 'Clear remembered peers list...'
  and 'Clear remembered applications list...', each with a Yes/No confirmation.
  Clearing peers refreshes the main window; clearing apps empties the global list.
- Self-test 'Remembered applications list is global + clearable' (round-trip,
  case-insensitive dedupe, clear); the dialog accessibility audit covers the two
  new buttons (names + mnemonics, no clash). Gate 37/37.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/SelfTest.cs

@@ -69,6 +69,7 @@ internal static class SelfTest
         RunStep(results, "Service network presence (reachable + shell teardown)", ServiceNetworkPresenceReachable);
         RunStep(results, "Service reachability-gated sending (drop dead peers, re-arm recovered)", ServiceReachabilityGating);
         RunStep(results, "Send-app capture change-detection (catch an app the instant it opens)", SendAppCaptureChangeDetection);
+        RunStep(results, "Remembered applications list is global + clearable", RememberedApplicationsGlobal);
         RunStep(results, "Service registration args", ServiceRegistrationArgs);
         RunStep(results, "Recording engine (all formats + source gate + mono)", RecordingEngine);
         RunStep(results, "Recording split tracks (per-peer + own)", RecordingSplitTracks);
@@ -1116,7 +1117,7 @@ internal static class SelfTest
             ("Recording settings", () => new RecordingSettingsDialog(new RecordingSettings())),
             ("Preferences", () => new PreferencesDialog(
                 new RemSoundSettingsStore("RemSound"), null,
-                () => false, _ => { }, () => { }, () => 0, () => { }, () => { }, () => { }, _ => { },
+                () => false, _ => { }, () => { }, () => 0, () => { }, () => { }, () => { }, () => { }, () => { }, _ => { },
                 () => (default(RouterMappingStatus), (IPEndPoint?)null, ""),
                 _ => { }, _ => { })),
             ("Service profile", () => new ServiceProfileDialog(RemSound.Core.Profile.NewBlank(), false)),
@@ -1551,6 +1552,27 @@ internal static class SelfTest
         return "signature stable when unchanged; changes when a ticked app opens/closes (drives instant capture)";
     }
 
+    /// <summary>Remembered applications are a GLOBAL, machine-wide list (like remembered peers), not
+    /// per-profile — a shared "apps I send" address book — and can be cleared (the Preferences button).
+    /// Verifies the store round-trips, dedupes case-insensitively to lower-case, and clears.</summary>
+    private static string? RememberedApplicationsGlobal()
+    {
+        var store = new RemSoundSettingsStore("RemSound");
+        var original = store.LoadRememberedApplications().ToList();
+        try
+        {
+            store.SaveRememberedApplications(new[] { "VLC", "Firefox", "vlc" });
+            var loaded = store.LoadRememberedApplications();
+            Check(loaded.Count == 2, $"remembered apps must dedupe case-insensitively (got {loaded.Count})");
+            Check(loaded.All(a => a == a.ToLowerInvariant()), "remembered app names must be stored lower-case");
+
+            store.SaveRememberedApplications(Array.Empty<string>());
+            Check(store.LoadRememberedApplications().Count == 0, "clearing must empty the remembered applications list");
+            return "global remembered applications: round-trip, case-insensitive dedupe, and clear";
+        }
+        finally { store.SaveRememberedApplications(original); }
+    }
+
     private static int FreeUdpPort()
     {
         using var s = new System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork,