fix(server): preserve provider usage in persisted turns

Merge terminal provider updates with stored context usage before replacing the SQLite payload. Keep newer usage reports authoritative and verify the persisted projection after reload.

Finding: R07 follow-up

Model: GPT-5.6 Sol via Codex
9b73ff4415Julius Marminge committed on 9/18/2026, 12:49:53 AM· committed by Julius Marmingeparent8875388
2 files changedLine totals unavailable