Harden payment settlement and result delivery #111

Goal

Make payment settlement, cancellation, and result delivery reliable across disconnects, retries, and shutdowns.

Scope

• Harden adapter settlement verification and cancellation cleanup.
• Recover missed settlement notifications through bounded reconciliation.
• Preserve result routing across payment waits and reconnects.
• Define stream ownership and cleanup on completion, cancellation, and shutdown.
• Expose distinct settlement, authorization, execution, and delivery outcomes.
• Add release qualification coverage for the complete payment lifecycle.

Acceptance

• Settlement is verified before paid execution; duplicate notifications cannot trigger duplicate execution.
• Cancellation and shutdown release adapter listeners, timers, and streams.
• Missed notifications and ambiguous settlement outcomes are reconciled without creating another invoice.
• Paid results retain their intended recipient and encryption context.
• Delivery failures are observable without automatically repeating paid execution.
• Tests cover adapter failures, disconnects, settlement races, routing, and resource cleanup.
• Concurrent tests, typecheck, lint, build, and export checks pass; live-provider validation limits are documented.

Dependencies

#108 and #110. Covers B04, B07, B10, B12, and B13.

Boundaries

No automatic refunds or reruns of consumed execution rights. Protocol and guide updates remain in next PR for separation of concerns.