[codex] Propagate rate limit reached type (#18227)

## Summary

First PR in the split from #17956.

- adds the core/app-server `RateLimitReachedType` shape
- maps backend `rate_limit_reached_type` into Codex rate-limit snapshots
- carries the field through app-server notifications/responses and
generated schemas
- updates existing constructors/tests for the new optional field

## Validation

- `cargo test -p codex-backend-client`
- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-app-server rate_limits`
- `cargo test -p codex-tui workspace_`
- `cargo test -p codex-tui status_`
- `just fmt`
- `just fix -p codex-backend-client`
- `just fix -p codex-app-server-protocol`
- `just fix -p codex-app-server`
- `just fix -p codex-tui`

codex-rs/core/src/session/tests.rs

@@ -2070,6 +2070,7 @@ async fn set_rate_limits_retains_previous_credits() {
             balance: Some("10.00".to_string()),
         }),
         plan_type: Some(codex_protocol::account::PlanType::Plus),
+        rate_limit_reached_type: None,
     };
     state.set_rate_limits(initial.clone());
 
@@ -2088,6 +2089,7 @@ async fn set_rate_limits_retains_previous_credits() {
         }),
         credits: None,
         plan_type: None,
+        rate_limit_reached_type: None,
     };
     state.set_rate_limits(update.clone());
 
@@ -2100,6 +2102,7 @@ async fn set_rate_limits_retains_previous_credits() {
             secondary: update.secondary,
             credits: initial.credits,
             plan_type: initial.plan_type,
+            rate_limit_reached_type: None,
         })
     );
 }
@@ -2176,6 +2179,7 @@ async fn set_rate_limits_updates_plan_type_when_present() {
             balance: Some("15.00".to_string()),
         }),
         plan_type: Some(codex_protocol::account::PlanType::Plus),
+        rate_limit_reached_type: None,
     };
     state.set_rate_limits(initial.clone());
 
@@ -2190,6 +2194,7 @@ async fn set_rate_limits_updates_plan_type_when_present() {
         secondary: None,
         credits: None,
         plan_type: Some(codex_protocol::account::PlanType::Pro),
+        rate_limit_reached_type: None,
     };
     state.set_rate_limits(update.clone());
 
@@ -2202,6 +2207,7 @@ async fn set_rate_limits_updates_plan_type_when_present() {
             secondary: update.secondary,
             credits: initial.credits,
             plan_type: update.plan_type,
+            rate_limit_reached_type: None,
         })
     );
 }

codex-rs/core/src/state/session_tests.rs

@@ -87,6 +87,7 @@ async fn set_rate_limits_defaults_limit_id_to_codex_when_missing() {
         secondary: None,
         credits: None,
         plan_type: None,
+        rate_limit_reached_type: None,
     });
 
     assert_eq!(
@@ -114,6 +115,7 @@ async fn set_rate_limits_defaults_to_codex_when_limit_id_missing_after_other_buc
         secondary: None,
         credits: None,
         plan_type: None,
+        rate_limit_reached_type: None,
     });
     state.set_rate_limits(RateLimitSnapshot {
         limit_id: None,
@@ -126,6 +128,7 @@ async fn set_rate_limits_defaults_to_codex_when_limit_id_missing_after_other_buc
         secondary: None,
         credits: None,
         plan_type: None,
+        rate_limit_reached_type: None,
     });
 
     assert_eq!(
@@ -157,6 +160,7 @@ async fn set_rate_limits_carries_credits_and_plan_type_from_codex_to_codex_other
             balance: Some("50".to_string()),
         }),
         plan_type: Some(codex_protocol::account::PlanType::Plus),
+        rate_limit_reached_type: None,
     });
 
     state.set_rate_limits(RateLimitSnapshot {
@@ -170,6 +174,7 @@ async fn set_rate_limits_carries_credits_and_plan_type_from_codex_to_codex_other
         secondary: None,
         credits: None,
         plan_type: None,
+        rate_limit_reached_type: None,
     });
 
     assert_eq!(
@@ -189,6 +194,7 @@ async fn set_rate_limits_carries_credits_and_plan_type_from_codex_to_codex_other
                 balance: Some("50".to_string()),
             }),
             plan_type: Some(codex_protocol::account::PlanType::Plus),
+            rate_limit_reached_type: None,
         })
     );
 }

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

@@ -2375,7 +2375,8 @@ async fn token_count_includes_rate_limits_snapshot() {
                     "resets_at": 1704074400
                 },
                 "credits": null,
-                "plan_type": null
+                "plan_type": null,
+                "rate_limit_reached_type": null
             }
         })
     );
@@ -2426,7 +2427,8 @@ async fn token_count_includes_rate_limits_snapshot() {
                     "resets_at": 1704074400
                 },
                 "credits": null,
-                "plan_type": null
+                "plan_type": null,
+                "rate_limit_reached_type": null
             }
         })
     );
@@ -2500,7 +2502,8 @@ async fn usage_limit_error_emits_rate_limit_event() -> anyhow::Result<()> {
             "resets_at": null
         },
         "credits": null,
-        "plan_type": null
+        "plan_type": null,
+        "rate_limit_reached_type": null
     });
 
     let submission_id = codex

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

@@ -1033,7 +1033,8 @@ async fn responses_websocket_usage_limit_error_emits_rate_limit_event() {
                     "resets_at": null
                 },
                 "credits": null,
-                "plan_type": null
+                "plan_type": null,
+                "rate_limit_reached_type": null
             }
         })
     );