Remove auto-start: launcher owns the app lifecycle

The TeslaConsole launcher starts and stops RIOJoy, so the app no longer
registers any auto-start entry:
- install-rio.ps1: drop the HKLM ...\Run registration and the post-install
  launch (and the -NoLaunch param).
- Tray: remove the "Start with Windows" menu item and delete AutoStartManager
  (HKCU ...\Run writer).
- AppConfig: drop the now-inert AutoStart field (+ test).
- Docs (PLAN.md, README-DEPLOY.txt) updated to reflect launcher-managed start/stop.

uninstall-rio.ps1 still clears any leftover Run entry from older auto-starting
builds. Solution builds; 241 tests pass.

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

tests/RioJoy.Core.Tests/Profiles/ConfigStoreTests.cs

@@ -15,7 +15,6 @@ public class ConfigStoreTests
             DefaultPlasmaComPort = "COM4",
             NativeGameExecutables = { "firestorm.exe", "redplanet.exe" },
             NeutralProfileName = "Desktop",
-            AutoStart = true,
             Profiles =
             {
                 new RioProfile
@@ -35,7 +34,6 @@ public class ConfigStoreTests
 
         Assert.Equal("COM3", back.DefaultRioComPort);
         Assert.Equal(new[] { "firestorm.exe", "redplanet.exe" }, back.NativeGameExecutables);
-        Assert.True(back.AutoStart);
 
         RioProfile p = Assert.Single(back.Profiles);
         Assert.Equal("Doom", p.Name);