Avoid redundant TUI redraws while streaming (#34049)

## What changed

- Redraw assistant and plan stream tails only when a completed line changes the visible tail.
- Cache the first reasoning header and update the status indicator only when its visible state changes, while restoring the cached header if the indicator is recreated.
- Keep regular commit ticks able to clear stale stream tails.

## Testing

- Add coverage for unchanged partial deltas, changed newline-delimited tails, reasoning-header redraws, recreated status indicators, stale plan tails, and history-line draw scheduling.

GitOrigin-RevId: 9016175f97ef2db2edc2fd5ba13a4d731dc2d98c

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

@@ -917,19 +917,22 @@ impl BottomPane {
 
     /// Update the status indicator header (defaults to "Working") and details below it.
     ///
-    /// Passing `None` clears any existing details. No-ops if the status indicator is not active.
+    /// Passing `None` clears any existing details. Returns whether the active status indicator
+    /// was updated and requested a redraw.
     pub(crate) fn update_status(
         &mut self,
         header: String,
         details: Option<String>,
         details_capitalization: StatusDetailsCapitalization,
         details_max_lines: usize,
-    ) {
+    ) -> bool {
         if let Some(status) = self.status.as_mut() {
             status.update_header(header);
             status.update_details(details, details_capitalization, details_max_lines.max(1));
             self.request_redraw();
+            return true;
         }
+        false
     }
 
     /// Show the transient "press again to quit" hint for `key`.