Let a caller supply the storage backend to annual_cli.main()

[mgazza]

What

annual_cli.main() gains an optional storage_factory, called as storage_factory(work_dir, log) — exactly how StorageLocalFiles is constructed today, so the default is that class itself and the command line behaves as it always has.

def main(argv=None, storage_factory=StorageLocalFiles):
    ...
    storage = storage_factory(args.work_dir, log)

Why

StorageBase is already an abstraction: annual_weather.py and annual_tariff.py only ever call self.storage.load() / save(), and AnnualPredictor uses whatever storage it is handed. But this entry point hard-coded the one implementation, so running the annual tool against a different backend meant forking the CLI — or reimplementing main(), and with it the --machine stdout/stderr contract. That last part is the fiddly bit worth not duplicating: the redirect_stdout guard that stops a stray print() from anything predictor.run() pulls in from corrupting the single JSON object a parent process parses off stdout.

The motivating case is embedding the annual tool in a long-lived service. There, a per-process work dir means every process re-downloads the same immutable ERA5 and Octopus data, none of it can be shared between them, and the duplicated requests land on the rate APIs. Pointing several processes at one shared backend (Redis, S3, a database) fixes both — and with this, that needs a factory rather than a fork.

Scope

Two lines of behaviour change, plus a docstring. No change to the CLI, its arguments, or its output. Nothing else in the file moves.

Testing

Added to tests/test_annual_cli.py, in the existing style:

• the default still constructs a StorageLocalFiles — so a plain command-line run is unchanged
• a supplied factory's storage reaches AnnualPredictor, and the factory receives --work-dir and the run's log callable

I checked the new assertions genuinely fail without the change (TypeError: main() got an unexpected keyword argument 'storage_factory') rather than passing vacuously.

Suites run and passing: annual_cli, annual_cli_machine, annual_cli_machine_end_to_end, annual_job, storage.

black 23.11.0 and ruff 0.11.4 — the versions pinned in .pre-commit-config.yaml — both report no changes. (The commit itself was made with --no-verify only because the pre-commit binary on this machine has a broken install; the hooks themselves were run by hand.)