Add model availability NUX metadata (#12972)

- replace show_nux with structured availability_nux model metadata
- expose availability NUX data through the app-server model API
- update shared fixtures and tests for the new field

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

@@ -237,6 +237,7 @@ async fn model_change_from_image_to_text_strips_prior_image_content() -> Result<
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,
@@ -395,6 +396,7 @@ async fn model_switch_to_smaller_model_updates_token_context_window() -> Result<
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,

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

@@ -339,6 +339,7 @@ fn test_remote_model(slug: &str, priority: i32) -> ModelInfo {
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,

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

@@ -602,6 +602,7 @@ async fn remote_model_friendly_personality_instructions_with_feature() -> anyhow
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,
@@ -710,6 +711,7 @@ async fn user_turn_personality_remote_model_template_includes_update_message() -
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,

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

@@ -297,6 +297,7 @@ async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,
@@ -534,6 +535,7 @@ async fn remote_models_apply_remote_base_instructions() -> Result<()> {
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,
@@ -995,6 +997,7 @@ fn test_remote_model_with_policy(
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy,
         supports_parallel_tool_calls: false,

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

@@ -403,6 +403,7 @@ async fn stdio_image_responses_are_sanitized_for_text_only_model() -> anyhow::Re
                 default_reasoning_summary: ReasoningSummary::Auto,
                 support_verbosity: false,
                 default_verbosity: None,
+                availability_nux: None,
                 apply_patch_tool_type: None,
                 truncation_policy: TruncationPolicyConfig::bytes(10_000),
                 supports_parallel_tool_calls: false,

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

@@ -664,6 +664,7 @@ async fn view_image_tool_returns_unsupported_message_for_text_only_model() -> an
         default_reasoning_summary: ReasoningSummary::Auto,
         support_verbosity: false,
         default_verbosity: None,
+        availability_nux: None,
         apply_patch_tool_type: None,
         truncation_policy: TruncationPolicyConfig::bytes(10_000),
         supports_parallel_tool_calls: false,