feat: cluster reliability (leader failover, crash rejoin, key exchange) + auth/users + canvas/forwards enhancements + comprehensive README + API docs

- Cluster: forwardToNext offline detection (leader+non-leader), WatchLeader 1s heartbeat fallback, 409 for standalone nodes, Node.NodeKey key exchange via token ring, ClusterPeers persistence + auto-rejoin, Forward delegates to forwardToNext (bugfix)
- Auth: Basic Auth (flag-creds fast path) + bcrypt users (admin/viewer) + Bearer API keys (read/write/admin scope)
- Frontend: UsersView (accounts+API keys), ClusterView (ring/nodeKey/tasks/topology/log), StatusView (group management, per-proxy status), CanvasView (edge toggle/group), PortEdge (disabled/group labels)
- API: handlers split (canvas/forwards/users/logs), canvas export/import, forwards group start/stop/assign/delete, cluster endpoints
- Docs: comprehensive README rewrite (all flags/APIs/auth/cluster), docs/cluster-api.md (cluster management API reference)
- Deploy: run-cluster.sh now 4-node ring + 1 isolated standalone, test-forward.sh updated for 4 nodes
- Removed plan.md (design notes consolidated into README + API docs)

internal/process/process.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"sort"
 	"sync"
 	"syscall"
 	"time"
@@ -272,6 +273,20 @@ func (m *Manager) Status(name string) (Status, bool) {
 	return m.getStatus(w), true
 }
 
+// ListWorkers returns the names of all workers currently under management
+// (running, starting, crashed-but-supervised, etc.), sorted for stable output.
+// Stopped workers are removed from the map and not listed.
+func (m *Manager) ListWorkers() []string {
+	m.mu.Lock()
+	out := make([]string, 0, len(m.workers))
+	for name := range m.workers {
+		out = append(out, name)
+	}
+	m.mu.Unlock()
+	sort.Strings(out)
+	return out
+}
+
 // StopAll stops all workers (used on manager shutdown).
 func (m *Manager) StopAll() {
 	m.mu.Lock()