feat: establish Orbit models, migrations and development baseline

weave/model/poll_policy.go

@@ -0,0 +1,32 @@
+package model
+
+import (
+	"errors"
+	"time"
+)
+
+var (
+	ErrPollExhausted = errors.New("poll budget exhausted; reconciliation required")
+	ErrPollInFlight  = errors.New("a poll round is still in flight")
+	ErrPollResolved  = errors.New("poll already resolved")
+	ErrPollNotDue    = errors.New("poll interval has not elapsed")
+)
+
+// NextRound 用数据库时间检查已锁定的查询快照。调用方还必须核验执行门控，
+// 并在同一事务中写入计数、唯一轮次及对应的 Pulse 任务。
+// 下一查询时间为空表示持久化暂挂，不能视为允许立即发起查询。
+func (p PollState) NextRound(now time.Time) (uint32, error) {
+	if p.ResolvedAt != nil {
+		return 0, ErrPollResolved
+	}
+	if p.MaxRounds == 0 || p.UsedRounds >= p.MaxRounds || !now.Before(p.DeadlineAt) {
+		return 0, ErrPollExhausted
+	}
+	if p.CurrentTaskID != nil {
+		return 0, ErrPollInFlight
+	}
+	if p.NextPollAt == nil || now.Before(*p.NextPollAt) {
+		return 0, ErrPollNotDue
+	}
+	return p.UsedRounds + 1, nil
+}