AP three-way match exceptions and accrual recommendations

Analyze AP three-way match exceptions for {period_end_date}.

Inputs:
- PO data: {po_data}
- Receiving/GRN data: {receiving_data}
- Invoice register: {invoice_register}
- GRNI/received-not-invoiced balance: {grni_balance}
- Tolerances: {price_qty_tolerances}

Deliver:
1) Exceptions table: PO#, Vendor, Item, Qty/Price mismatch, $ impact, Suggested action.
2) GRNI rollforward and recommended accrual entries (if needed).
3) Process improvements (root causes, controls, automation ideas).

Classify exceptions as: timing, pricing, receiving error, duplicate invoice, or vendor issue.