// Package contract defines the shared full-sync domain and service boundaries.
// It contains no Redis, filesystem, replay execution, or HTTP handler code.
//
// Legacy queue models remain in internal/queue/zset until adapters adopt this
// package. Their existing JSON fields are retained here; new run fields are
// optional so historical records still decode. Missing extended counters mean
// unknown, not a reconstructed total. FailedCount is the historical terminal
// count for a run; cleaning source failures changes PendingFailureCount only.
//
// Implementations must preserve these boundaries: run-local Redis keys share
// one hash tag, global indexes do not; archive summaries never contain card
// details; cursors are opaque and scoped to the original query; replay writes
// are idempotent and fenced by a lease before source cleanup is allowed.
package contract