refactor(server): clean up close listener and avoid writing 499 to dead socket

Wrap the long-poll handler in try/finally to detach the req.raw close
listener on every resolution path, and use reply.hijack() on the aborted
branch so Fastify does not attempt to write to a socket that's already
closed (which would otherwise emit per-disconnect log noise once the
watcher relaunch loop is busy). Behavior on the wire is unchanged for
the four documented status codes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

node/src/server.ts

@@ -145,26 +145,30 @@ export async function buildServer(cfg: DaemonConfig, store: MailboxStore): Promi
       }
 
       const ac = new AbortController();
-      req.raw.on("close", () => ac.abort());
+      const onClose = (): void => ac.abort();
+      req.raw.once("close", onClose);
+      try {
+        const result = await store.waitForMessage(name, timeoutS * 1000, ac.signal);
 
-      const result = await store.waitForMessage(name, timeoutS * 1000, ac.signal);
-
-      if (result.kind === "message") {
-        const msg = rowToMessage(result.message);
-        reply.code(200);
-        return { ...msg, sentAt: msg.sentAt.toISOString() };
+        if (result.kind === "message") {
+          const msg = rowToMessage(result.message);
+          reply.code(200);
+          return { ...msg, sentAt: msg.sentAt.toISOString() };
+        }
+        if (result.kind === "renamed") {
+          reply.code(409);
+          return { reason: "renamed", to: result.to };
+        }
+        if (result.kind === "timeout") {
+          reply.code(204);
+          return reply.send();
+        }
+        // aborted — client gone; hand control to Fastify without writing to the dead socket.
+        reply.hijack();
+        return;
+      } finally {
+        req.raw.off("close", onClose);
       }
-      if (result.kind === "renamed") {
-        reply.code(409);
-        return { reason: "renamed", to: result.to };
-      }
-      if (result.kind === "timeout") {
-        reply.code(204);
-        return reply.send();
-      }
-      // aborted — client gone, no response needed (Fastify will swallow).
-      reply.code(499);
-      return reply.send();
     },
   );