Function resolve_station_temperature 

pub fn resolve_station_temperature(
    temperature_c: f64,
    altitude_m: f64,
) -> Option<f64>

Resolve the temperature override for an air-density calculation, mirroring resolve_station_pressure.

• An explicitly-supplied temperature is authoritative (returned as Some).
• When temperature is left at the sea-level standard default (15 °C) while a real altitude is given, the caller meant “standard atmosphere at this altitude”: return None so calculate_atmosphere applies the ICAO lapse-rate temperature for that altitude (≈ −6.5 °C/km).

Without this, --altitude with the default temperature held the air at 15 °C, which under-estimates density (warm air is thinner) by ~2.4% at 1 km up to ~7% at 3 km versus the standard atmosphere — validated against py_ballisticcalc, which derives both temperature and pressure from altitude. The 0.1 °C tolerance matches the 59 °F = 15.0 °C default exactly, and >1 m avoids triggering at sea level. A shooter at a genuinely non-standard temperature at altitude should pass an explicit temperature (same contract as station pressure).