pss: auto-reopen subscription on Bee WebSocket close

Bee closes the pssSubscribe WebSocket after ~8s of idleness (or on any
transient hiccup). The previous handler only logged the close — so the
gateway silently went deaf to every ack/deliver envelope that arrived
after the first close, breaking every chat whose provider takes more
than a few seconds to respond. Re-open the subscription on close with a
short delay; cancel() now blocks further reopens.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/t4t/lib/swarm.ts

@@ -149,7 +149,18 @@ export class PssTransport {
 
   subscribe(args: PssSubscribeArgs): PssSubscription {
     const topic = Topic.fromString(args.topic)
-    return this.opts.bee.pssSubscribe(topic, {
+    // Bee's pssSubscribe is a WebSocket that Bee closes whenever it feels like
+    // (idle timeout, broker hiccup, transient WS reset). Without re-subscribe,
+    // the gateway misses every envelope after the first close — which silently
+    // breaks every job whose provider sends ack/deliver more than a few
+    // seconds after the chat request lands. Wrap the subscription in a
+    // self-healing loop: on close, log + reopen.
+    let cancelled = false
+    let current: PssSubscription | null = null
+    const RECONNECT_DELAY_MS = 500
+    const open = (): void => {
+      if (cancelled) return
+      current = this.opts.bee.pssSubscribe(topic, {
         onMessage: async msg => {
           try {
             const env = decodeEnvelope(msg.toUtf8())
@@ -171,8 +182,17 @@ export class PssTransport {
           this.opts.logger.error({err}, 'pss subscription error')
         },
         onClose: () => {
-        this.opts.logger.warn({topic: args.topic}, 'pss subscription closed')
+          this.opts.logger.warn({topic: args.topic}, 'pss subscription closed — reopening')
+          if (!cancelled) setTimeout(open, RECONNECT_DELAY_MS)
         },
       })
     }
+    open()
+    return {
+      cancel: () => {
+        cancelled = true
+        current?.cancel()
+      },
+    } as PssSubscription
+  }
 }