[docs] Remove misleading WithTerminal Shell option

src/frontend/src/content/docs/app-host/with-terminal.mdx

@@ -74,9 +74,12 @@ The terminal session is described by a set of options with sensible defaults:
 | ------------------- | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `Columns`           | `120`   | The initial number of columns for the terminal grid.                                                                                                            |
 | `Rows`              | `30`    | The initial number of rows for the terminal grid.                                                                                                               |
-| `Shell`             | `null`  | The shell to launch for the session. When `null`, the default is used: for containers this is typically `/bin/sh`; for executables the process itself is the terminal program. |
 | `ShowTerminalHost`  | `false` | Whether the hidden per-replica terminal host resources appear in the dashboard and CLI resource lists. Set to `true` to diagnose terminal-host startup or connectivity issues. |
 
+<Aside type="note">
+The resource being run is always the terminal program: for executables that's the process itself, and for containers it's the container's own process. There's no way to select a different shell to launch for the session—an earlier `Shell` option that appeared to do this was removed because it was never wired up to the underlying pseudo-terminal and had no effect.
+</Aside>
+
 <Tabs syncKey='aspire-lang'>
 <TabItem id='csharp' label='C#'>