Determine which model tier to prefer given current budget utilisation.
When utilisation is below softLimitRatio (default 0.8), no tier bias is
applied and routing proceeds normally. When at or above the soft limit,
the caller should prefer ECONOMY-tier agents and exclude PREMIUM.
Parameters
utilisation: number
Current budget utilisation ratio [0.0, 1.0]
softLimitRatio: number = 0.8
Soft limit threshold; default 0.8 (80 %)
Returns "ECONOMY"|null
'ECONOMY' when bias should be applied, null for no preference
Determine which model tier to prefer given current budget utilisation.
When utilisation is below
softLimitRatio(default 0.8), no tier bias is applied and routing proceeds normally. When at or above the soft limit, the caller should prefer ECONOMY-tier agents and exclude PREMIUM.