Create or reconcile 1–100 complete workflow bills as full snapshots. An
exact replay returns the same bill identities without an Accounting write;
a material update follows the bill's current lifecycle and approver-access
policy. Results preserve request order.

Validation and payment-destination preflight finish before Accounting.
Accounting commits the bill batch atomically, then Payments reconciles
destinations atomically, then bill events publish. A failure in a later
service does not roll back an earlier service's committed work.

Webhook event identity uses the persisted whole-second bill mutation
time. Two material updates to the same bill within one second can share a
deduplication key and suppress the later webhook. An exact no-op replay
cannot recover a missing event after the mutation has committed.

Requires scope: bills:manage.