Make radiation→ocean forcing hook live; rename radiative flux functions

[glwagner]

Summary

Two related cleanups around how radiation forces the ocean, prompted by tracing compute_radiative_forcing! and TwoColorRadiation.

1. compute_radiative_forcing! — from dead code to a live extension hook

Previously compute_radiative_forcing! was defined but never called, and its dispatch was backwards: the fallback was a no-op while the TwoColorRadiation method did host-side work that the in-kernel shortwave_radiative_forcing already does.

It's now the generic, overridable precompute hook for radiation models whose in-water absorption requires a vertical pass over ocean tracers (e.g. biogeochemical / chlorophyll-based schemes):

• generic compute_radiative_forcing!(radiation, coupled_model) — the overridable entry point (fallback no-op),
• compute_radiative_forcing!(::TwoColorRadiation, coupled_model) — explicit no-op (analytic absorption; its surface flux is set per-column in the flux kernel),
• called from compute_radiation_ocean_fluxes! right before the kernel launch!.

Behavior today is unchanged (no-op for the only existing scheme and for nothing), but the extension point is now genuinely wired in. Also fixes notation Iˢʷ → ℐˢʷ to match the script-I used in the kernel (ℐꜜˢʷ/ℐₜˢʷ/ℐꜛˡʷ).

2. Rename the radiative flux family: apply_air_* → compute_radiation_*

The fluxes are sourced from the radiation component (coupled_model.radiation), not the atmosphere — these functions never touch coupled_model.atmosphere. The new names use the component-pair form parallel to the turbulent compute_atmosphere_ocean_fluxes!:

Old	New
apply_air_sea_radiative_fluxes!	compute_radiation_ocean_fluxes!
apply_air_sea_ice_radiative_fluxes!	compute_radiation_sea_ice_fluxes!
apply_air_land_radiative_fluxes!	compute_radiation_land_fluxes!

Files renamed (git mv, history preserved); all definitions, _-prefixed kernels, (::Any)/{<:Nothing} fallbacks, includes, and doc/comment references updated. grep confirms no stale apply_air_* tokens remain.

Left intentionally unchanged: air_sea_interface_radiation_state (describes the radiation state at the surface interface — distinct concept, separate scope).

Test plan

• CI (no compile check run locally — no Julia REPL available; pure token rename + a no-op hook call, definition/call sites updated symmetrically)

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