Adds two additive, flag-gated routing refinements on top of the §7 scoring
core; both default OFF so the deterministic claim path is unchanged.
- FLEET_COST_ROUTING: soft engineQuality term (weight 0.4) biases routing
toward the historically cheaper/faster engine, derived from per-engine
insights.costUsd + run duration. No-history engines stay neutral, so the
nudge can only demote demonstrably costly engines, never penalise new ones.
- FLEET_ENGINE_BREAKER: per-(factory, engine) circuit breaker. releaseLease
always records outcomes (observable via /fleet/metrics engineBreakers);
when enabled, an OPEN pair is routed around. Only ever restricts the
candidate set — never forces a route.
The scheduler stays pure: history lookup + availability gate are injected
predicates. New engineQuality term contributes 0 unless a lookup is supplied,
preserving every existing score/breakdown.
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
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