v0.31.0

Changelog

• 29f67f9 Fix the Gemini tool-replay 400, and stop it from costing 12 minutes of silence (#8)
• 556fe78 feat(models): a delegated model pin for sub-agents and scouts
• 8d85a4f feat(policy): a typed behavior-policy layer
• a0e29a0 models: retire Kimi K2.6 and K2.7 Code (#7)