Aerosol activation has numerical instabilities

[tapios]

The ARG parameterization (max_supersaturation) is numerically unstable for certain atmospheric conditions.

For example:

• Line 167: sqrt(α * w / G) - when α * w / G becomes negative
• Line 180: (ζ / η)^ap.p1 - when intermediate values become -Inf

These (and other issues) need numerical guardrails and tests.