Route calibration cycle models through reasoning tier

[sene1337]

Summary

Routes hindsight calibration-cycle model selection through the model-tier resolver instead of hardcoded/native Anthropic defaults:

• adds phase-specific config keys for propose_takes, grade_takes, and calibration_profile
• falls back to models.tier.reasoning when a phase-specific key is unset
• registers the new keys so gbrain config set ... works without --force
• updates docs/tests around the new routing behavior

Why

Private-gateway or local-first operators can set one reasoning-tier model and have all calibration-cycle phases use it. Without this, the propose/grade/profile phases can drift back to native Anthropic defaults even when the rest of the brain is configured for private routing.

Verification

• bun test test/propose-takes.test.ts test/grade-takes.test.ts test/grade-takes-ensemble.test.ts test/calibration-profile.test.ts test/cycle-model-routing.test.ts test/config-set.test.ts — 110 pass
• bun run typecheck