fix: wait for nick confirmation before joining channels

Send NICK and wait for server confirmation (up to 10s) before
issuing JOIN commands, ensuring channels are joined under the
correct identity.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/bouncer/network.py

@@ -161,6 +161,8 @@ class Network:
         self._connect_nick: str = ""
         # Visible hostname reported by server
         self.visible_host: str | None = None
+        # Signals that a NICK change was confirmed by the server
+        self._nick_confirmed: asyncio.Event = asyncio.Event()
         # Channel state: topic + names per channel
         self.topics: dict[str, str] = {}
         self.names: dict[str, set[str]] = {}
@@ -335,8 +337,14 @@ class Network:
             desired = _random_nick()
         log.info("[%s] switching nick: %s -> %s (host=%s)", self.cfg.name, self.nick, desired,
                  self.visible_host or "unknown")
+        self._nick_confirmed.clear()
         await self.send_raw("NICK", desired)
-        # nick will be updated when we get the NICK confirmation from server
+
+        # Wait for server to confirm the nick change before joining
+        try:
+            await asyncio.wait_for(self._nick_confirmed.wait(), timeout=10)
+        except asyncio.TimeoutError:
+            log.warning("[%s] nick change not confirmed in 10s, joining anyway", self.cfg.name)
 
         # Join configured channels
         if self.cfg.autojoin and self.cfg.channels:
@@ -392,6 +400,7 @@ class Network:
             if old_nick == self.nick:
                 log.info("[%s] nick changed: %s -> %s", self.cfg.name, old_nick, new_nick)
                 self.nick = new_nick
+                self._nick_confirmed.set()
 
         elif msg.command == "JOIN" and msg.prefix:
             nick = msg.prefix.split("!")[0]