Opening Entries Preview

Validate (possibly user-edited) opening entries before the atomic create (stateless).

Carries the in-progress journal entries (accountant shape: [{header, lines:[…]}]) plus the target-FY chart so the same render-time validation used post-onboarding (export.validate.validate_document) runs against the edited document.

opening_balance_account_number is the clearing account the opening entries balance against. The accountant only synthesizes it into the proposal (never into the document chart), and the atomic create seeds it via ensure_opening_balance_account_for_fiscal_year right before posting — so the preview must add it to the validated chart too, or it rejects the clearing line as LINE_ACCOUNT_NOT_IN_CHART and over-blocks "Create".

Per-entry validation warnings + whether the edited document is safe to post.

postable is True only when there are no blocking warnings (unbalanced entry, account not in the target-FY chart, non-positive amount, non-base currency) — the wizard gates "Create" on it. The GL post remains the final authority at create time.