terminal: Persist pinned tabs in terminal (#31921)

Closes #31098

Release Notes:

- Fixed terminal pinned tab state not persisting across restarts.

crates/terminal_view/src/terminal_panel.rs

@@ -325,7 +325,6 @@ impl TerminalPanel {
                     .ok();
             }
         }
-
         Ok(terminal_panel)
     }
 
@@ -393,6 +392,9 @@ impl TerminalPanel {
             pane::Event::Focus => {
                 self.active_pane = pane.clone();
             }
+            pane::Event::ItemPinned | pane::Event::ItemUnpinned => {
+                self.serialize(cx);
+            }
 
             _ => {}
         }