feat(core): add durable mint swap orchestration foundation

[igbopharaoh]

Work in progress

Summary

• define the durable Mint Swap parent model, accounting invariants, prepared-plan fingerprint,
  fenced preparation lease, CAS contract, and operation-event outbox
• add parent-owned mint and melt commands that commit authorization before remote I/O and apply
  results atomically afterward
• split swap-then-melt execution into durable pre-swap and melt authorization phases
• add an optional Mint Swap repository capability with rollback-safe, concurrency-safe memory
  transactions
• add shared adapter contracts for capability absence, CAS, ownership, rollback, due ordering,
  outbox idempotency, and concurrent root writes

Dependency

Important

This draft depends on #400 and must not be marked ready or merged before Slice 1 lands.

Slice 1 provides the canonical BOLT11 accounting, locked quote/NUT-20 behavior, dispatch policy,
and broad-log rules consumed by this foundation. After #400 merges, this branch must be rebased
onto master, preserving those protocol changes and resolving the overlapping mint/melt seams.

Scope boundaries

• Mint Swap remains dormant: no Manager/API activation, scheduler, processor, history, or React
  surface is added
• persistent SQL and IndexedDB implementations remain in Slice 3
• coordinator and restart recovery remain in Slice 4

Draft integration checklist

• rebase onto master after feat(core): add protocol and secure BOLT11 foundations #400 merges
• bind owned destination preparation to the locked quote's persisted NUT-20 key
• apply destination issuance through Slice 1's canonical quote accounting
• confirm the restricted owned-mint remote context preserves custom-handler compatibility
• enforce legal parentExecutionPhase combinations through the shared child invariant
• rerun the combined Slice 1 and Slice 2 suites

Verification

• bun run --filter='@cashu/coco-core' typecheck
• bun run --filter='@cashu/coco-adapter-tests' typecheck
• bun run --filter='@cashu/coco-core' build
• bun run --filter='@cashu/coco-adapter-tests' build
• bun run --filter='@cashu/coco-core' test:unit
• bun test ./src/test/contract.test.ts from packages/sqlite-bun

No changeset is included because release metadata is assigned to the final rollout slice.

Closes #366.

[changeset-bot]

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