launcher: Rec-Room-styled UI; PowerShell-free patcher; Launch button

UI redesign:
- Warm coral + teal palette over deep purple-navy (closer to Rec Room's
  marketing aesthetic). New wordmark gradient (coral -> pink -> teal).
- Chunky 18px rounded cards on the first-run wizard with per-mode
  accent tinting (coral for host, teal for join) and clear CTAs.
- Form fields wrapped in elevated panels with sectional titles + pill
  status chips in the header (HOST MODE / JOIN MODE / SETTINGS).
- Drop-shadow effects on primary buttons + cards for depth.

Patcher rewrite:
- ClientPatcher.cs no longer shells out to PowerShell; the launcher
  unzips MelonLoader, copies the DorkNet plugin DLL, and renders the
  user-data config template — all in C# in-process.
- Patcher zip now driven by a manifest.json at root (schema v1).
  Per-version branches publish: manifest.json + MelonLoader.zip +
  DorkNet.ClientMod.dll + config template.
- RELEASES.md updated with the new MelonLoader manifest contract and
  the placeholder substitution rules.

Rec Room launch path:
- New Backend/RecRoomLauncher.cs runs Recroom_Release.exe directly
  from the picked install folder's parent dir (no Steam).
- 'Launch Rec Room' button appears after a successful patch in both
  host + join modes.

launcher/MainWindow.xaml.cs

@@ -238,7 +238,8 @@ public partial class MainWindow : Window
             });
             JoinCodeText.Text = code;
             JoinCodePanel.Visibility = Visibility.Visible;
-            HostStatusText.Text = $"Hosting at {publicUrl}";
+            HostStatusText.Text = $"Hosting at {publicUrl}. Share the join code below or launch Rec Room to test.";
+            HostLaunchBtn.Visibility = Visibility.Visible;
         }
         catch (Exception ex)
         {
@@ -253,6 +254,7 @@ public partial class MainWindow : Window
         await ShutdownServerAsync();
         HostStartBtn.IsEnabled = true;
         HostStopBtn.Visibility = Visibility.Collapsed;
+        HostLaunchBtn.Visibility = Visibility.Collapsed;
         JoinCodePanel.Visibility = Visibility.Collapsed;
         HostStatusText.Text = "Stopped.";
     }
@@ -325,12 +327,22 @@ public partial class MainWindow : Window
                 payload.PhotonAppId, payload.PhotonVoiceAppId, payload.Host);
             if (!patch.Ok) { ShowError("Patcher failed: " + Truncate(patch.Log, 500)); return; }
 
-            JoinStatusText.Text = "Patched. Launch Rec Room from Steam to connect.";
+            JoinStatusText.Text = $"Patched and ready. Connecting to {payload.Host}. " +
+                "Click Launch Rec Room when you're ready to play.";
+            JoinLaunchBtn.Visibility = Visibility.Visible;
         }
         catch (Exception ex) { ShowError(ex.Message); }
         finally { RefreshJoinReadiness(); }
     }
 
+    private void OnLaunchRecRoom(object sender, RoutedEventArgs e)
+    {
+        if (string.IsNullOrEmpty(_state.RecRoomPath))
+        { ShowError("Pick your Rec Room install first."); return; }
+        if (!RecRoomLauncher.TryLaunch(_state.RecRoomPath, out var error))
+            ShowError(error);
+    }
+
     // ── Helpers ─────────────────────────────────────────────────────────
     private static string FormatProgress(string label, DownloadProgress p)
     {