agent: Only show the MCP configuration modal in the active window (#32450)

We were previously displaying this modal in all open Zed windows if
triggered. That was a bit annoying because I had to go to each window
individually to close it, which meant doing it multiple times. 😅

Release Notes:

- agent: Fixed the MCP configuration modal to show only in the active
window.

crates/agent/src/context_server_configuration.rs

@@ -71,6 +71,10 @@ fn show_configure_mcp_modal(
     window: &mut Window,
     cx: &mut Context<'_, Workspace>,
 ) {
+    if !window.is_window_active() {
+        return;
+    }
+
     let context_server_store = workspace.project().read(cx).context_server_store();
     let repository: Option<SharedString> = manifest.repository.as_ref().map(|s| s.clone().into());