[apply_patch] freeform apply_patch tool (#2576)

## Summary
GPT-5 introduced the concept of [custom
tools](https://platform.openai.com/docs/guides/function-calling#custom-tools),
which allow the model to send a raw string result back, simplifying
json-escape issues. We are migrating gpt-5 to use this by default.

However, gpt-oss models do not support custom tools, only normal
functions. So we keep both tool definitions, and provide whichever one
the model family supports.

## Testing
- [x] Tested locally with various models
- [x] Unit tests pass

codex-rs/core/src/rollout.rs

@@ -132,6 +132,8 @@ impl RolloutRecorder {
                 | ResponseItem::LocalShellCall { .. }
                 | ResponseItem::FunctionCall { .. }
                 | ResponseItem::FunctionCallOutput { .. }
+                | ResponseItem::CustomToolCall { .. }
+                | ResponseItem::CustomToolCallOutput { .. }
                 | ResponseItem::Reasoning { .. } => filtered.push(item.clone()),
                 ResponseItem::Other => {
                     // These should never be serialized.
@@ -194,6 +196,8 @@ impl RolloutRecorder {
                     | ResponseItem::LocalShellCall { .. }
                     | ResponseItem::FunctionCall { .. }
                     | ResponseItem::FunctionCallOutput { .. }
+                    | ResponseItem::CustomToolCall { .. }
+                    | ResponseItem::CustomToolCallOutput { .. }
                     | ResponseItem::Reasoning { .. } => items.push(item),
                     ResponseItem::Other => {}
                 },
@@ -317,6 +321,8 @@ async fn rollout_writer(
                         | ResponseItem::LocalShellCall { .. }
                         | ResponseItem::FunctionCall { .. }
                         | ResponseItem::FunctionCallOutput { .. }
+                        | ResponseItem::CustomToolCall { .. }
+                        | ResponseItem::CustomToolCallOutput { .. }
                         | ResponseItem::Reasoning { .. } => {
                             writer.write_line(&item).await?;
                         }