Function spawn_downgrade_in_terminal 

pub fn spawn_downgrade_in_terminal(
    app: &mut AppState,
    items: &[PackageItem],
) -> bool

What: Spawn the downgrade tool in an external terminal without Pacsea-managed password piping.

Inputs:

• app: Mutable application state.
• items: Packages to downgrade.

Output:

• true if the downgrade was spawned (or an error modal shown); false otherwise.

Details:

• Used in interactive auth mode where the external terminal handles privilege authentication.
• Builds a {tool} downgrade <packages> command (no password piping).
• Clears downgrade state and shows a toast message.