AiNative turn efficiency:
- auto_finalize_single_tool: single staged-write turns skip the closing planner round-trip
- Single-shot tool repeat guard: a re-planned already-succeeded declared tool finalizes instead of re-executing (fixes 48s / 5-duplicate-preview turns)
- turn_deadline_seconds: typed failure instead of a FatalError past max_execution_time
- Cap-proof per-turn outcome accounting
- Prompt-size: snapshot outcome compaction + replayed-history turn-context stripping