order.sx — reserve -> await-payment -> fulfil as a flow-on-sx flow carrying
only the order-id; the SX driver services each request by appending to the
persist ledger. order-begin! creates+reserves and suspends at payment;
order-settle! (webhook) resumes -> fulfils, idempotent on replay
(:already-settled). order-flow-restart! simulates a process restart Scheme-side
and the suspended order resumes with the ledger intact. Composes all three
substrates: minikanren pricing -> flow lifecycle -> persist ledger.
Total 153/153 across 9 suites.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>