Support self-serve Business ProLite accounts (#35785)

## What changed

- Recognize `self_serve_business_prolite` across authentication, account and rate-limit APIs, generated schemas, workspace classification, status display, cloud configuration gating, and usage-limit messaging.
- Keep the Python SDK's `PlanType` enum compatible with non-empty string values introduced by newer Codex runtimes while preserving its known constants.

## Testing

- Cover token parsing, account reads and notifications, backend rate-limit mapping, workspace behavior, error formatting, and Python SDK response coercion for the new plan value.

GitOrigin-RevId: 70bc17a7c4ba4028cb10e4333cc1f2ac64da361f

codex-rs/protocol/src/error_tests.rs

@@ -351,6 +351,21 @@ fn usage_limit_reached_error_formats_business_plan_without_reset() {
     }
 }
 
+#[test]
+fn usage_limit_reached_error_formats_self_serve_business_prolite_plan() {
+    let err = UsageLimitReachedError {
+        plan_type: Some(PlanType::Known(KnownPlan::SelfServeBusinessProLite)),
+        resets_at: None,
+        rate_limits: Some(Box::new(rate_limit_snapshot())),
+        promo_message: None,
+        rate_limit_reached_type: None,
+    };
+    assert_eq!(
+        err.to_string(),
+        "You've hit your usage limit. To get more access now, send a request to your admin or try again later."
+    );
+}
+
 #[test]
 fn usage_limit_reached_error_formats_self_serve_business_usage_based_plan() {
     let err = UsageLimitReachedError {