Console: survive a launcher-dropped connection during product installs

The launcher drops RPC sessions idle >30s (easily hit while the operator sits
in the install dialogs), but a dropped socket still reports Connected until an
I/O fails. InstallProductWorker then skipped its reopen, streamed the archive
on the fresh out-of-band connection, and died on the first progress poll —
and the install-completed handler registered launch entries without checking
e.Error, so AddApp's disconnected-guard exception crashed the whole console.

- PodInfo.EnsureConnectionAlive: probe an "open" connection with a Ping and
  reconnect when it is dead; used by the install and uninstall workers.
- SiteManagement.PodInfo_InstallProductCompleted: register launch entries only
  on success, and surface registration failures as the row's Install Failed
  state instead of an unhandled exception.
- Regression test pins the premise + recovery against vPOD's launcher server
  (stale socket reports open, Ping exposes it, reconnect restores service).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Console/tests/TeslaConsole.DiffTests/VPodLauncherServerTests.cs

@@ -199,6 +199,27 @@ namespace TeslaConsole.DiffTests
             Assert.Empty(mLauncher.GetInstalledApps());
         }
 
+        [Fact]
+        public void Dropped_Session_Still_Reports_Open_Until_Probed_Then_Reconnect_Works()
+        {
+            // The launcher (and vPOD) drops sessions idle >30s. Simulate the drop
+            // server-side and pin the premise PodInfo.EnsureConnectionAlive relies
+            // on: the client socket still REPORTS open until an I/O fails...
+            mServer.Stop();
+            mServer.Start(mKey);
+            Thread.Sleep(100); // let the FIN arrive
+            Assert.True(mClient.IsOpen, "a dropped-but-unused connection should still report open (the stale state)");
+
+            // ...the cheap Ping probe is what exposes the dead connection...
+            Assert.ThrowsAny<Exception>(() => mClient.Ping(DateTime.UtcNow));
+
+            // ...and close + reopen (EnsureConnectionAlive's recovery) restores service.
+            mClient.Close();
+            mClient.Open(new IPEndPoint(IPAddress.Loopback, mPort), mKey);
+            var now = new DateTime(2026, 7, 9, 12, 0, 0, DateTimeKind.Utc);
+            Assert.Equal(now, mClient.Ping(now));
+        }
+
         [Fact]
         public void Installed_Apps_Persist_Across_Launcher_Restart()
         {