feat: rotate sessions on occupancy threshold

internal/orchestrator/orchestrator.go

@@ -14,6 +14,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"sync"
+	"time"
 )
 
 type Worktrees interface {
@@ -68,6 +69,61 @@ type Coordinator struct {
 	sessions  map[string]herdr.Session
 }
 
+// Monitor performs conservative hard-threshold rotation. The adapter owns
+// the handoff creation; the coordinator only publishes its content address
+// and frees the lease for pickup by the router.
+func (c *Coordinator) Monitor(ctx context.Context, hard float64, interval time.Duration) error {
+	if interval <= 0 {
+		interval = 30 * time.Second
+	}
+	t := time.NewTicker(interval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-t.C:
+			c.rotate(ctx, hard)
+		}
+	}
+}
+func (c *Coordinator) rotate(ctx context.Context, hard float64) {
+	c.mu.Lock()
+	sessions := make(map[string]herdr.Session, len(c.sessions))
+	for id, s := range c.sessions {
+		sessions[id] = s
+	}
+	c.mu.Unlock()
+	for taskID, session := range sessions {
+		task, ok := c.Store.Task(taskID)
+		if !ok || task.State != domain.StateLeased {
+			continue
+		}
+		a, err := c.Adapters.Adapter(session.Harness)
+		if err != nil {
+			continue
+		}
+		occupancy, err := a.Occupancy(session)
+		if err != nil || occupancy < hard {
+			continue
+		}
+		ref, err := a.Release(ctx, session)
+		if err != nil {
+			continue
+		}
+		if ref == "" {
+			continue
+		}
+		b, _ := json.Marshal(map[string]string{"handoff_ref": ref, "reason": "threshold"})
+		e := domain.Event{ID: domain.NewID(), Type: "TaskReleased", TaskID: taskID, Version: task.Version + 1, Payload: b}
+		if c.Store.Append(e) == nil {
+			c.mu.Lock()
+			delete(c.sessions, taskID)
+			c.mu.Unlock()
+		}
+	}
+}
+
 func (c *Coordinator) Start(ctx context.Context, e domain.Event) error {
 	if e.Type != "TaskLeased" {
 		return nil