File to create: `spec/services/feed_profile_validator_spec.rb`
`FeedProfileValidator` is currently uncovered. Service-level unit tests:
- happy path (all required columns present)
- missing required column → raises
- extra columns ignored
- empty header set → raises
Pairs with S4 (collapse two plucks; add error base class) — TDD them together.
File to create: `spec/services/feed_profile_validator_spec.rb`
`FeedProfileValidator` is currently uncovered. Service-level unit tests:
Pairs with S4 (collapse two plucks; add error base class) — TDD them together.