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/core/tests/suite/model_switching.rs

@@ -106,6 +106,7 @@ fn test_model_info(
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,
@@ -818,6 +819,7 @@ async fn model_switch_to_smaller_model_updates_token_context_window() -> Result<
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,

codex-rs/core/tests/suite/models_cache_ttl.rs

@@ -341,6 +341,7 @@ fn test_remote_model(slug: &str, priority: i32) -> ModelInfo {
         supported_in_api: true,
         priority,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,

codex-rs/core/tests/suite/personality.rs

@@ -579,6 +579,7 @@ async fn remote_model_friendly_personality_instructions_with_feature() -> anyhow
         supported_in_api: true,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: Some(ModelMessages {
@@ -687,6 +688,7 @@ async fn user_turn_personality_remote_model_template_includes_update_message() -
         supported_in_api: true,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: Some(ModelMessages {

codex-rs/core/tests/suite/remote_models.rs

@@ -533,6 +533,7 @@ async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,
@@ -789,6 +790,7 @@ async fn remote_models_apply_remote_base_instructions() -> Result<()> {
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: remote_base.to_string(),
         model_messages: None,
@@ -1279,6 +1281,7 @@ fn test_remote_model_with_policy(
         supports_search_tool: false,
         priority,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,

codex-rs/core/tests/suite/rmcp_client.rs

@@ -1283,6 +1283,7 @@ async fn stdio_image_responses_are_sanitized_for_text_only_model() -> anyhow::Re
                 supported_in_api: true,
                 priority: 1,
                 additional_speed_tiers: Vec::new(),
+                service_tiers: Vec::new(),
                 upgrade: None,
                 base_instructions: "base instructions".to_string(),
                 model_messages: None,

codex-rs/core/tests/suite/spawn_agent_description.rs

@@ -67,6 +67,7 @@ fn test_model_info(
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,

codex-rs/core/tests/suite/view_image.rs

@@ -1085,6 +1085,7 @@ async fn view_image_tool_returns_unsupported_message_for_text_only_model() -> an
         supports_search_tool: false,
         priority: 1,
         additional_speed_tiers: Vec::new(),
+        service_tiers: Vec::new(),
         upgrade: None,
         base_instructions: "base instructions".to_string(),
         model_messages: None,