fix(tui): remove unused next_id field from ToastManager

The next_id field became dead code when toast notifications were disabled
and push() was changed to a no-op returning 0 immediately. This fixes the
Clippy dead_code warning in CI.

Author: echobt

src/cortex-tui-components/src/toast.rs

@@ -234,8 +234,6 @@ pub enum ToastPosition {
 pub struct ToastManager {
     /// Active toasts (newest first)
     toasts: Vec<Toast>,
-    /// Counter for generating unique toast IDs
-    next_id: u64,
     /// Maximum number of toasts to display at once
     max_visible: usize,
     /// Screen position for toast display
@@ -251,7 +249,6 @@ impl ToastManager {
     pub fn new() -> Self {
         Self {
             toasts: Vec::new(),
-            next_id: 1,
             max_visible: 5,
             position: ToastPosition::TopRight,
         }

src/cortex-tui/src/widgets/toast.rs

@@ -233,8 +233,6 @@ pub enum ToastPosition {
 pub struct ToastManager {
     /// Active toasts (newest first)
     toasts: Vec<Toast>,
-    /// Counter for generating unique toast IDs
-    next_id: u64,
     /// Maximum number of toasts to display at once
     max_visible: usize,
     /// Screen position for toast display
@@ -250,7 +248,6 @@ impl ToastManager {
     pub fn new() -> Self {
         Self {
             toasts: Vec::new(),
-            next_id: 1,
             max_visible: 5,
             position: ToastPosition::TopRight,
         }