Normalize image detail for the receiving model (#44249)

## Why

Switching models can send images from conversation history with `detail: original` to a model that does not support it.

## What changed

Normalize image details on request copies using the receiving model's capabilities. Downgrade `original` to `high` when unsupported, covering user messages and function and custom tool outputs. Preserve stored image details so switching back to a supporting model retains `original`, and continue stripping details for Responses Lite.

## Testing

Expand unit coverage across image detail values and model capabilities. Extend integration coverage for model switches within and between turns, text-only models, and resumed and forked threads, including assertions that persisted tool outputs remain unchanged.

GitOrigin-RevId: 2561651ea74f045e00f708ae53771a41dcd49c94

codex-rs/app-server/tests/suite/v2/turn_start.rs

@@ -16,6 +16,7 @@ use app_test_support::format_with_current_shell_display;
 use app_test_support::write_chatgpt_auth;
 use app_test_support::write_mock_responses_config_toml_with_chatgpt_base_url;
 use app_test_support::write_models_cache;
+use app_test_support::write_models_cache_with_models;
 use codex_app_server::INPUT_TOO_LARGE_ERROR_CODE;
 use codex_app_server::INVALID_PARAMS_ERROR_CODE;
 use codex_app_server_protocol::AdditionalContextEntry;
@@ -76,6 +77,7 @@ use codex_core::test_support::all_model_presets;
 use codex_exec_server::LOCAL_ENVIRONMENT_ID;
 use codex_features::Feature;
 use codex_login::AuthCredentialsStoreMode;
+use codex_models_manager::model_info::model_info_from_slug;
 use codex_protocol::config_types::CollaborationMode;
 use codex_protocol::config_types::ModeKind;
 use codex_protocol::config_types::MultiAgentMode;
@@ -141,6 +143,9 @@ async fn run_local_image_turn(detail: Option<ImageDetail>) -> Result<Vec<Value>>
 
     let codex_home = TempDir::new()?;
     MockResponsesConfig::new(&server.uri()).write(codex_home.path())?;
+    let mut model = model_info_from_slug("mock-model");
+    model.supports_image_detail_original = true;
+    write_models_cache_with_models(codex_home.path(), vec![model]).await?;
 
     let mut mcp = TestAppServer::builder()
         .with_codex_home(codex_home.path())