Rewrite oversized tool outputs during remote compaction (#26251)

## Why

When trying to fit history under compaction limit rewrite output items
instead of removing them entirely. Otherwise we're breaking
incrementality in relation to the previous response.

codex-rs/core/src/context_manager/history.rs

@@ -174,16 +174,6 @@ impl ContextManager {
         }
     }
 
-    pub(crate) fn remove_last_item(&mut self) -> bool {
-        if let Some(removed) = self.items.pop() {
-            normalize::remove_corresponding_for(&mut self.items, &removed);
-            self.history_version = self.history_version.saturating_add(1);
-            true
-        } else {
-            false
-        }
-    }
-
     pub(crate) fn replace(&mut self, items: Vec<ResponseItem>) {
         self.items = items;
         self.history_version = self.history_version.saturating_add(1);
@@ -734,15 +724,6 @@ fn is_model_generated_item(item: &ResponseItem) -> bool {
     }
 }
 
-pub(crate) fn is_codex_generated_item(item: &ResponseItem) -> bool {
-    matches!(
-        item,
-        ResponseItem::FunctionCallOutput { .. }
-            | ResponseItem::ToolSearchOutput { .. }
-            | ResponseItem::CustomToolCallOutput { .. }
-    ) || matches!(item, ResponseItem::Message { role, .. } if role == "developer")
-}
-
 pub(crate) fn is_user_turn_boundary(item: &ResponseItem) -> bool {
     let ResponseItem::Message { role, content, .. } = item else {
         return false;

codex-rs/core/src/context_manager/history_tests.rs

@@ -651,28 +651,6 @@ fn remove_first_item_removes_matching_call_for_output() {
     assert_eq!(h.raw_items(), vec![]);
 }
 
-#[test]
-fn remove_last_item_removes_matching_call_for_output() {
-    let items = vec![
-        user_msg("before tool call"),
-        ResponseItem::FunctionCall {
-            id: None,
-            name: "do_it".to_string(),
-            namespace: None,
-            arguments: "{}".to_string(),
-            call_id: "call-delete-last".to_string(),
-        },
-        ResponseItem::FunctionCallOutput {
-            call_id: "call-delete-last".to_string(),
-            output: FunctionCallOutputPayload::from_text("ok".to_string()),
-        },
-    ];
-    let mut h = create_history_with_items(items);
-
-    assert!(h.remove_last_item());
-    assert_eq!(h.raw_items(), vec![user_msg("before tool call")]);
-}
-
 #[test]
 fn replace_last_turn_images_replaces_tool_output_images() {
     let items = vec![

codex-rs/core/src/context_manager/mod.rs

@@ -5,6 +5,5 @@ pub(crate) mod updates;
 pub(crate) use history::ContextManager;
 pub(crate) use history::TotalTokenUsageBreakdown;
 pub(crate) use history::estimate_response_item_model_visible_bytes;
-pub(crate) use history::is_codex_generated_item;
 pub(crate) use history::is_user_turn_boundary;
 pub(crate) use history::truncate_function_output_payload;