Mirror WO PR #99's template-first approach for the Coupa PO processor. Two templates identified from a full 3,448-email triage:
- coupa_new_po (95.5%): scaffolded; fails closed to the LLM until extract_new_po lands.
- coupa_cancellation (2.9%): implemented.
Nested contract with recursive validation, Decimal money, and a fail-closed gate. Derived fields (site_code/trade/fiscal_year) are deferred to a shared post-stage. Comments, revisions, multi-line, and non-USD emails fall back to Bedrock. docs/po-template-parser.md records the investigation, decisions, and remaining work.
Signed-off-by: Adam Moussa <166072409+amoussa1229@users.noreply.github.com>
