Auto compact at ~90% (#5292)

Users now hit a window exceeded limit and they usually don't know what
to do. This starts auto compact at ~90% of the window.

codex-rs/tui/src/bottom_pane/chat_composer.rs

@@ -108,7 +108,7 @@ pub(crate) struct ChatComposer {
     custom_prompts: Vec<CustomPrompt>,
     footer_mode: FooterMode,
     footer_hint_override: Option<Vec<(String, String)>>,
-    context_window_percent: Option<u8>,
+    context_window_percent: Option<i64>,
 }
 
 /// Popup state – at most one can be visible at any time.
@@ -1511,7 +1511,7 @@ impl ChatComposer {
         self.is_task_running = running;
     }
 
-    pub(crate) fn set_context_window_percent(&mut self, percent: Option<u8>) {
+    pub(crate) fn set_context_window_percent(&mut self, percent: Option<i64>) {
         if self.context_window_percent != percent {
             self.context_window_percent = percent;
         }

codex-rs/tui/src/bottom_pane/footer.rs

@@ -17,7 +17,7 @@ pub(crate) struct FooterProps {
     pub(crate) esc_backtrack_hint: bool,
     pub(crate) use_shift_enter_hint: bool,
     pub(crate) is_task_running: bool,
-    pub(crate) context_window_percent: Option<u8>,
+    pub(crate) context_window_percent: Option<i64>,
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -221,8 +221,8 @@ fn build_columns(entries: Vec<Line<'static>>) -> Vec<Line<'static>> {
         .collect()
 }
 
-fn context_window_line(percent: Option<u8>) -> Line<'static> {
-    let percent = percent.unwrap_or(100);
+fn context_window_line(percent: Option<i64>) -> Line<'static> {
+    let percent = percent.unwrap_or(100).clamp(0, 100);
     Line::from(vec![Span::from(format!("{percent}% context left")).dim()])
 }
 

codex-rs/tui/src/bottom_pane/mod.rs

@@ -70,7 +70,7 @@ pub(crate) struct BottomPane {
     status: Option<StatusIndicatorWidget>,
     /// Queued user messages to show under the status indicator.
     queued_user_messages: Vec<String>,
-    context_window_percent: Option<u8>,
+    context_window_percent: Option<i64>,
 }
 
 pub(crate) struct BottomPaneParams {
@@ -357,7 +357,7 @@ impl BottomPane {
         }
     }
 
-    pub(crate) fn set_context_window_percent(&mut self, percent: Option<u8>) {
+    pub(crate) fn set_context_window_percent(&mut self, percent: Option<i64>) {
         if self.context_window_percent == percent {
             return;
         }