fix(tui): remove duplicate context statusline item (#18054)

Addresses #18045

Problem: `/statusline` exposed both `context-remaining` and
`context-remaining-percent` after conflicting PRs attempted to address
the same context-status issue, including #17637, allowing duplicate
footer segments.

Solution: Remove the duplicate `context-remaining-percent` status-line
item and update status-line tests and snapshots to use only canonical
`context-remaining`.

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

@@ -66,10 +66,6 @@ pub(crate) enum StatusLineItem {
     /// Percentage of context window remaining.
     ContextRemaining,
 
-    /// Percentage of context window remaining.
-    #[strum(to_string = "context-remaining-percent")]
-    ContextRemainingPercent,
-
     /// Percentage of context window used.
     ///
     /// Also accepts the legacy `context-usage` config value.
@@ -119,9 +115,6 @@ impl StatusLineItem {
             StatusLineItem::ContextRemaining => {
                 "Percentage of context window remaining (omitted when unknown)"
             }
-            StatusLineItem::ContextRemainingPercent => {
-                "Percentage of context window remaining (omitted when unknown)"
-            }
             StatusLineItem::ContextUsed => {
                 "Percentage of context window used (omitted when unknown)"
             }
@@ -321,7 +314,7 @@ mod tests {
     }
 
     #[test]
-    fn context_remaining_is_separate_selectable_id() {
+    fn context_remaining_is_selectable_id() {
         assert_eq!(
             "context-remaining".parse::<StatusLineItem>(),
             Ok(StatusLineItem::ContextRemaining)
@@ -332,18 +325,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn context_remaining_percent_is_separate_selectable_id() {
-        assert_eq!(
-            StatusLineItem::ContextRemainingPercent.to_string(),
-            "context-remaining-percent"
-        );
-        assert_eq!(
-            "context-remaining-percent".parse::<StatusLineItem>(),
-            Ok(StatusLineItem::ContextRemainingPercent)
-        );
-    }
-
     #[test]
     fn preview_uses_runtime_values() {
         let preview_data = StatusLinePreviewData::from_iter([