Add a flag to skip column description inheritance

[nol107]

Problem:

Column description inheritance can introduce subtly inaccurate documentation. A column may evolve between layers (renamed logic, different grain, filtered subset), making the upstream description misleading when inherited by a child model. Some columns are also not worth documenting at every layer (e.g., generic intermediate plumbing columns), yet carrying a wrong inherited description is worse than having no description at all.

Current behavior:

When a child model has an empty column description, dbt-osmosis automatically inherits the description from the parent model. The existing --force-inherit-descriptions flag only controls whether to overwrite a child's existing description with the parent's — it does not prevent inheritance into empty columns.

Expected behavior:

There should be a way to opt out of description inheritance entirely, so that empty descriptions remain empty rather than being populated with potentially inaccurate upstream descriptions.

Suggested solution:

Add a --skip-inherit-descriptions flag that prevents inheriting descriptions into child columns, even when the child's description is empty. This would complement the existing --force-inherit-descriptions flag by covering the opposite use case.

I'd be happy to propose a PR if this direction makes sense.