break: replace muxed workers with 1:1 tunnels

Worker frames are now FrameType + payload; there is no stream id.
Each player gets its own worker conn. maxTunnels (default 256)
caps concurrent tunnels. The old maxConn pool size is ignored so
existing configs do not silently admit only a handful of players.

Resume, per-direction windows, the control session, and the
DATA-only shaper stay. A dropped worker still hangs that one
player and reattaches over a fresh conn.

Add a hub-side per-IP limiter for player intents only (default
8/s, burst 16, 64 concurrent). Unmatched hostnames consume a
token; Intent 17 is never counted. 0 disables each knob.

client/stats.go

@@ -57,11 +57,9 @@ type connStats struct {
 	framesOut atomic.Int64
 	writeErrs atomic.Int64
 
-	// Round-trip time of the mux heartbeat. The probe already carries a
+	// Round-trip time of the worker heartbeat. The probe already carries a
 	// timestamp that the peer echoes and both sides currently throw away, so
-	// this measures tunnel latency for no added cost — and it is the best signal
-	// available for head-of-line blocking, where one stream's backlog delays
-	// every other stream sharing the connection.
+	// this measures tunnel latency for no added cost.
 	mu      sync.Mutex
 	rttLast time.Duration
 	rttMin  time.Duration
@@ -137,22 +135,19 @@ func (c *Client) StatsLine() string {
 
 	live, parked := 0, 0
 	for _, wc := range conns {
-		wc.mu.Lock()
-		streams := make([]*Stream, 0, len(wc.streams))
-		for _, s := range wc.streams {
-			streams = append(streams, s)
-		}
-		wc.mu.Unlock()
-		live += len(streams)
-		for _, s := range streams {
-			s.mu.Lock()
-			if s.parked {
+		st := wc.getStream()
+		bound := 0
+		if st != nil {
+			bound = 1
+			live++
+			st.mu.Lock()
+			if st.parked {
 				parked++
 			}
-			s.mu.Unlock()
+			st.mu.Unlock()
 		}
 
-		fmt.Fprintf(&b, " | conn%d streams=%d", wc.id, len(streams))
+		fmt.Fprintf(&b, " | conn%d bound=%d", wc.id, bound)
 		if cs := wc.stats; cs != nil {
 			_, mn, avg, mx := cs.rtt()
 			fmt.Fprintf(&b, " frames=%d/%d rtt=%s/%s/%s",
@@ -162,7 +157,7 @@ func (c *Client) StatsLine() string {
 			}
 		}
 	}
-	fmt.Fprintf(&b, " | streams=%d parked=%d", live, parked)
+	fmt.Fprintf(&b, " | tunnels=%d parked=%d", live, parked)
 	return b.String()
 }
 
@@ -189,7 +184,10 @@ func (s *Stream) logSummary() {
 
 func (p *WorkerPool) snapshot() []*WorkerConn {
 	p.mu.Lock()
-	conns := append([]*WorkerConn(nil), p.conns...)
+	conns := make([]*WorkerConn, 0, len(p.conns))
+	for wc := range p.conns {
+		conns = append(conns, wc)
+	}
 	p.mu.Unlock()
 	sort.Slice(conns, func(i, j int) bool { return conns[i].id < conns[j].id })
 	return conns