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

sdk/python/src/openai_codex/generated/v2_all.py

@@ -2505,7 +2505,7 @@ class PlanDeltaNotification(BaseModel):
     turn_id: Annotated[str, Field(alias="turnId")]
 
 
-class PlanType(Enum):
+class PlanType(str, Enum):
     free = "free"
     go = "go"
     plus = "plus"
@@ -2519,6 +2519,15 @@ class PlanType(Enum):
     edu = "edu"
     unknown = "unknown"
 
+    @classmethod
+    def _missing_(cls, value: object) -> PlanType | None:
+        if not isinstance(value, str) or not value:
+            return None
+        member = str.__new__(cls, value)
+        member._name_ = value
+        member._value_ = value
+        return member
+
 
 class PluginAuthPolicy(Enum):
     on_install = "ON_INSTALL"