fix(interactive): use library LaunchProcess instead of custom pty bypass

The custom Porta.Pty bypass (own read loop, key tunneling, resize sync) rendered
wrong, lagged, and dropped input. The spike proved TerminalControl.LaunchProcess()
renders correctly and stays responsive, so hand pty/input/render/resize/focus back
to the library. PtyTerminalSession shrinks to a thin wrapper: apply descriptor.Env
process-wide (Porta.Pty inherits the process env; no per-launch env seam), set
Process/Args/StartingDirectory, LaunchProcess(). Process="" still suppresses the
control's auto-launch so exactly one process starts.

src/ClaudeDo.Ui/Views/InteractiveTerminalView.axaml

@@ -7,8 +7,9 @@
              x:Name="Root">
   <!--
     Process="" suppresses TerminalView.OnLoaded's built-in auto-launch (it otherwise spawns its
-    own cmd.exe/bash the moment this control loads). We drive the pty ourselves via
-    PtyTerminalSession/InteractiveTerminalViewModel instead.
+    own cmd.exe/bash the moment this control loads). PtyTerminalSession sets Process/Args/
+    StartingDirectory to our real target and calls TerminalControl.LaunchProcess() exactly once,
+    once the view model's descriptor is known (see AttachControl/Start).
   -->
   <term:TerminalControl x:Name="TerminalHost" Process="" />
 </UserControl>