Fix post-merge runtime errors; clean stale ohmic/tidal references

- Project.toml: relax julia compat to >= 1.10 (was ~1.11), move
  Coverage from [deps] to [extras]/[targets], remove stale compat
  pins (Test, Coverage)
- atmosphere.jl: remove orphan ediv_add allocation (field does not
  exist in Atmos_t after merge from main)
- energy.jl: replace atmos.layer_mass[i] with inline dp/g column
  mass computation in deep_heating!() :mass normalisation (layer_mass
  field removed in main)
- default.toml: remove ohmic/tidal/power config entries, keep only
  the 8 simplified deep_heating parameters
- test_deep_heating.jl: remove ohmic_eff, tidal_power_auto, and
  generic_power test cases; strip mechanism kwarg from remaining
  cases to match simplified DeepHeatingParams

Author: Andrew Cheng-An Hsieh