Add premium forecast endpoints to SDK

[nik-solcast]

Adds premium PV and wind forecast endpoints while preserving compatibility-mode SDK structure. Tests: 35 passed.

[michaelf-solcast]

Changes look ok to me. Is the motivation for all the unrelated docstring changes, to get these aligned with that the automated generation approach would provide, to make it easier to use the automated generation in future?

The documentation at docs/forecast.md also needs to be updated to reference the premium options.

[nik-solcast]

@michaelf-solcast yes, my intention is to align with the docstring as over time the SDK tells different story from the code and no one is updating it manually. If there is value in keeping different or shorter versions in some cases, that could also be handled.

[michaelf-solcast]

Doco looks ok. Happy to approve the changes, provision on you having tested them in python, but I don't have permission to approve (need to be maintainer?)

[nik-solcast]

from solcast import forecast
response = forecast.premium_pv_power("8423-7088-7b9b-cc72")
print(response.code, response.success); print(response.to_dict()['forecasts'][:5])

200 True
[{'power': 0.0, 'period_end': '2026-08-31T01:30:00+00:00', 'period': 'PT30M'}, {'power': 0.0, 'period_end': '2026-08-31T02:00:00+00:00', 'period': 'PT30M'}, {'power': 0.0, 'period_end': '2026-08-31T02:30:00+00:00', 'period': 'PT30M'}, {'power': 0.0, 'period_end': '2026-08-31T03:00:00+00:00', 'period': 'PT30M'}, {'power': 0.0, 'period_end': '2026-08-31T03:30:00+00:00', 'period': 'PT30M'}]

response = forecast.premium_wind_power("a123-eb37-365f-2edb")
print(response.code, response.success); print(response.to_dict()['forecasts'][:5])

200 True
[{'power': 2.3724, 'period_end': '2026-08-31T01:30:00+00:00', 'period': 'PT30M'}, {'power': 2.4307, 'period_end': '2026-08-31T02:00:00+00:00', 'period': 'PT30M'}, {'power': 2.4892, 'period_end': '2026-08-31T02:30:00+00:00', 'period': 'PT30M'}, {'power': 2.531, 'period_end': '2026-08-31T03:00:00+00:00', 'period': 'PT30M'}, {'power': 2.7497, 'period_end': '2026-08-31T03:30:00+00:00', 'period': 'PT30M'}]