v0.2.4 — two new venues, one of which settles

Two new venue drivers. One of them settles at a batch tier and has the receipt
to prove it; the other is blocked on billing and has a receipt saying that.

Google Gemini — settles

| 2026-08-24-gemini-1 | 5 jobs | gemini:batch | $0.00919 | $0.00460
| $0.00460 (50.0%) | 5/5 |

Zero sync fallbacks, 2m36s end to end. The first venue outside OpenAI and
Anthropic here to capture the spread rather than record why it could not.

It is also the first venue that is not OpenAI-shaped, so the driver carries a
real translation layer:

• messages → contents/parts, assistant → model, and a system message
  lifted onto system_instruction rather than sent as a turn
• params → a typed config (max_tokens → max_output_tokens), with unknown keys
  dropped rather than forwarded, because an unknown key is a hard error found
  hours after a batch is submitted
• no custom_id: the job id rides in the request's metadata and comes back on
  the response
• twelve job states, with PARTIALLY_SUCCEEDED treated as a completion so the
  work that succeeded is not discarded

Thinking tokens are billed as output and counted as output.
usageMetadata reports thoughtsTokenCount apart from candidatesTokenCount;
a receipt reading only the visible answer would have reported roughly a tenth of
this bill.

Mistral — driver complete, tier closed

POST /v1/batch/jobs answers 402 … enable billing via the console. Everything
else works: file upload with purpose=batch is reachable, sync completions
return 200, and all 24 jobs of 2026-08-24-mistral-1 settled through the sync
fallback at list, capturing nothing. That is on the ledger next to the rows that
captured 50%.

The driver handles Mistral's own shape: one model per batch (taken at create and
applied to the whole file, so a mixed batch is refused by name), timeout_hours
as the completion window, and seven job states with TIMEOUT_EXCEEDED mapped to
failed rather than cancelled.

Prices

Mistral and Google rows join the bundled sheet, keyed on family prefixes so a
dated SKU inherits its family. Gemini 3.7/3.6 Flash carry their introductory
rates with the 2027-01-01 step-up as PromoNotes.

Two prefix hazards are handled rather than left to be discovered:
gemini-3.5-flash would otherwise swallow gemini-3.5-flash-lite, and
gemini-3.1-flash-lite is left off entirely because its id is a prefix of an
image model whose rate is not on the text sheet.

Upgrading

pip install -U offpeak
pip install "offpeak[gemini]"   # or [mistral]

No API changes. Both new venues are opt-in — their own extras, outside all,
outside default_venues().