Preserve image detail in app-server inputs (#20693)

## Summary

- Add optional image detail to user image inputs across core, app-server
v2, thread history/event mapping, and the generated app-server
schemas/types.
- Preserve requested detail when serializing Responses image inputs:
omitted detail stays on the existing `high` default, while explicit
`original` keeps local images on the original-resolution path.
- Support `high`/`original` consistently for tool image outputs,
including MCP `codex/imageDetail`, code-mode image helpers, and
`view_image`.

codex-rs/state/src/extract.rs

@@ -205,6 +205,7 @@ mod tests {
             images: Some(vec![]),
             local_images: vec![],
             text_elements: vec![],
+            ..Default::default()
         }));
 
         apply_rollout_item(&mut metadata, &item, "test-provider");
@@ -225,6 +226,7 @@ mod tests {
             images: Some(vec!["https://example.com/image.png".to_string()]),
             local_images: vec![],
             text_elements: vec![],
+            ..Default::default()
         }));
 
         apply_rollout_item(&mut metadata, &item, "test-provider");
@@ -248,6 +250,7 @@ mod tests {
             images: Some(vec![]),
             local_images: vec![],
             text_elements: vec![],
+            ..Default::default()
         }));
 
         apply_rollout_item(&mut metadata, &item, "test-provider");
@@ -287,6 +290,7 @@ mod tests {
             images: Some(vec![]),
             local_images: vec![],
             text_elements: vec![],
+            ..Default::default()
         }));
 
         apply_rollout_item(&mut metadata, &user_item, "test-provider");