1- Add model service tiers metadata (#20969)

## Why

The model list needs to carry display-ready service tier metadata so
clients can render tier choices with stable IDs, names, and
descriptions. A raw speed-tier string list is not enough for richer UI
copy or future tier labels.

## What changed

- Added `ModelServiceTier` to shared model metadata with string `id`,
`name`, and `description` fields.
- Added `service_tiers` to `ModelInfo` and `ModelPreset`, preserving
empty defaults for older cached model payloads.
- Exposed `serviceTiers` on app-server v2 `Model` responses and threaded
it through TUI app-server model conversion.
- Marked legacy `additional_speed_tiers` / `additionalSpeedTiers`
metadata as deprecated in source and generated schema output.
- Regenerated app-server protocol JSON schema and TypeScript fixtures,
including `ModelServiceTier.ts`.

## Verification

- Ran `just write-app-server-schema`.
- Did not run local tests per repo instruction; relying on PR CI.

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/tui/src/app_server_session.rs

@@ -111,6 +111,7 @@ use codex_protocol::models::PermissionProfile;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::openai_models::ModelAvailabilityNux;
 use codex_protocol::openai_models::ModelPreset;
+use codex_protocol::openai_models::ModelServiceTier;
 use codex_protocol::openai_models::ModelUpgrade;
 use codex_protocol::openai_models::ReasoningEffortPreset;
 use codex_utils_absolute_path::AbsolutePathBuf;
@@ -1046,6 +1047,15 @@ fn model_preset_from_api_model(model: ApiModel) -> ModelPreset {
             .collect(),
         supports_personality: model.supports_personality,
         additional_speed_tiers: model.additional_speed_tiers,
+        service_tiers: model
+            .service_tiers
+            .into_iter()
+            .map(|service_tier| ModelServiceTier {
+                id: service_tier.id,
+                name: service_tier.name,
+                description: service_tier.description,
+            })
+            .collect(),
         is_default: model.is_default,
         upgrade,
         show_in_picker: !model.hidden,

codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs

@@ -2453,6 +2453,7 @@ async fn model_picker_hides_show_in_picker_false_models_from_cache() {
         }],
         supports_personality: false,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         is_default: false,
         upgrade: None,
         show_in_picker,
@@ -2673,6 +2674,7 @@ async fn single_reasoning_option_skips_selection() {
         supported_reasoning_efforts: single_effort,
         supports_personality: false,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         is_default: false,
         upgrade: None,
         show_in_picker: true,