test: align auto-import style fixture coverage

[mattiamanzati]

Summary

• update the auto-import style consistency tests to use the mounted @effect-v4 Effect fixtures instead of synthetic package files where appropriate
• rewrite the barrel coverage to assert the full rewritten fix shapes from top-level effect barrel imports, including the qualified succeed call shape
• add a changeset for the test coverage update

Validation

• pnpm setup-repo
• pnpm lint
• pnpm check
• pnpm test