agent: Use current shell (#28470)

Release Notes:

- agent: Replace `bash` tool with `terminal` tool which uses the current
shell

---------

Co-authored-by: Bennet <bennet@zed.dev>
Co-authored-by: Antonio <antonio@zed.dev>

crates/terminal/src/terminal.rs

@@ -380,7 +380,7 @@ impl TerminalBuilder {
                     #[cfg(target_os = "windows")]
                     {
                         Some(alacritty_terminal::tty::Shell::new(
-                            util::retrieve_system_shell(),
+                            util::get_windows_system_shell(),
                             Vec::new(),
                         ))
                     }