mohdel v3.7.0

Added

• billingOf(modelId) from mohdel/providers returns how a model's calls are
  paid for: { kind: 'metered' | 'plan' | 'capacity', label?, usage? }. Every
  provider declares billing; an unknown provider throws.

Changed

• cost is 0 for plan (chatgpt/) and capacity (local/) providers, read
  from the declaration. A priced local/ entry, chat, embedding or
  transcription, now reports 0.
• mo ls and the mo ask summary show not metered · <label> in place of
  prices for chatgpt/ and local/ models.
• mo model check warns when a local/ entry carries prices.