Model choices now depend on your billing state

What

A new helper sorts each account into a billing state: pay_per_request, admin_billed, included_in_plan, needs_consent, needs_credits, out_of_credits or consented. Two model checks now use it.

• The automatic switch to a model with a larger context window, used when the conversation is about to be too long, now also calls Mar. Mar allows the switch when the model is not recognised, the account is pay-per-request or admin-billed, or you have agreed to extra usage and have credits. The old Bve(w) condition was removed.
• The path for Fable and similar models now applies when the model family's billing mode is neither pay_per_request nor included_in_plan.

Why

Accounts that have not agreed to extra usage, or have no credits, will likely no longer be moved to the bigger-context model automatically. That avoids charges you did not agree to. Which accounts see the Fable-specific behaviour now depends on how the account is billed.