Use herogold.argparse Argument for STORE_BOOL defaults instead of parser.set_defaults

[HEROgold]

From the review of #2:

parser.setdefaults work, however i'd like to update/use Argument class to handle this behaviour.

Current state

src/funcsort/main.py declares its flags declaratively:

sort_module = Argument("sort-module", action=Actions.STORE_BOOL, default=True, ...)
respect_dependencies = Argument("respect-dependencies", action=Actions.STORE_BOOL, default=True, ...)

but those default=True values are effectively dead, because line 48 overrides them:

parser.set_defaults(check=False, diff=False, recursive=True, sort_module=None, respect_dependencies=None)

The None sentinel is deliberate: it is what lets the config file win unless the user passes the flag explicitly (main.py:85-86). STORE_BOOL registers a --flag/--no-flag pair, and there is currently no way to express "unset" through Argument alone — hence the set_defaults escape hatch.

Desired state

The fix belongs in the herogold.argparse package: Argument / Actions.STORE_BOOL should support a tri-state default natively (True / False / unset), so main.py can drop parser.set_defaults entirely and keep the declarative _Cli block as the single source of truth.

Follow-up

When this is solved, re-review the config/CLI merge lines:

If we can simplify/couple args and settings, this line must be reviewed again.

main.py:85-86:

sort_module = settings.sort_module if args.sort_module is None else args.sort_module
respect_dependencies = settings.respect_dependencies if args.respect_dependencies is None else args.respect_dependencies

Related: #4 (config declaration boilerplate).