Add full purchase order agent tooling and supporting changes:
- Add server-side purchase-order-agent-service for scanning both stock and customer POs, with complete test coverage
- Add inline SKU and supplier SKU editing flows to stock order detail pages
- Update MCP API route to support new PO agent tools (purchase_orders.scan, diff, record_diff_report) and stock_purchase_items.list
- Fix flaky CollectionPoolPage tests by wrapping state-dependent assertions in waitFor
- Refactor CollectionPoolPage auto-collapse logic to avoid react-hooks lint trap and run exactly once on initial load
- Delete temporary .tmp-inspect-pool.mjs development script
