v0.13.1

Added

• Gemini 4 Argon (gemini-4-argon, 1M context, 64K output, thinking): $2 / $10 per 1M tokens, cached input $0.10,
  through 2026-11-30, and $4 / $20 / $0.20 from 2026-12-01 (a scheduled price); Batch at half; Google Search grounding
  $14 / 1,000 queries. Implicit caching only, so no storage rate. Served by the vendor and absent from the catalog until now.