No intellisense for enum name user,system generated as KnownEnum

[MaryGao]

see comments and playground, when generating the knownable items for enum key user,system there is no intellisense for it.

relevant tsp would be like

https://github.com/Azure/typespec-azure/blob/main/packages/typespec-azure-resource-manager/lib/common-types/types.tsp#L226-L241

/**
 * The intended executor of the operation; as in Resource Based Access Control (RBAC) and audit logs UX. Default value is "user,system"
 */
union Origin {
  /** Indicates the operation is initiated by a user. */
  user: "user",

  /** Indicates the operation is initiated by a system. */
  system: "system",

  /** Indicates the operation is initiated by a user or system. */
  `user,system`: "user,system",

  string,
}

another case would be there is no key defined in union

https://github.com/azure/typespec-azure/blob/main/packages/typespec-azure-resource-manager/lib/common-types/managed-identity.tsp#L62-L84

union ManagedServiceIdentityType {
  /** No managed identity. */
  "None",

  /** System assigned managed identity. */
  "SystemAssigned",

  /** User assigned managed identity. */
  "UserAssigned",

  /** System and user assigned managed identity. */
  @added(Versions.v3)
  @removed(Versions.v4)
  @added(Versions.v5)
  "SystemAssigned,UserAssigned",

  /** System and user assigned managed identity. */
  @added(Versions.v4)
  @removed(Versions.v5)
  "SystemAssigned, UserAssigned",

  string,
}