feat: persist invite-joined channels for auto-rejoin on connect

When the bot accepts an admin INVITE, the channel is stored in
bot.state under chanmgmt/autojoin:<channel>. On reconnect, persisted
channels are rejoined alongside configured ones. If the bot is kicked,
the channel is removed from the auto-rejoin list.

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

plugins/chanmgmt.py

@@ -85,6 +85,23 @@ async def cmd_mode(bot, message):
     await bot.mode(message.target, mode_str, *args)
 
 
+@event("001")
+async def on_connect(bot, message):
+    """Rejoin channels persisted from previous invite-joins."""
+    from derp.irc import format_msg
+
+    configured = set(bot.config["bot"]["channels"])
+    for key in bot.state.keys("chanmgmt"):
+        if not key.startswith("autojoin:"):
+            continue
+        channel = key[len("autojoin:"):]
+        if channel in configured:
+            continue
+        log.info("rejoining %s (autojoin)", channel)
+        await bot.join(channel)
+        await bot.conn.send(format_msg("WHO", channel))
+
+
 @event("INVITE")
 async def on_invite(bot, message):
     """Join a channel when invited by an admin or IRC operator."""
@@ -96,3 +113,17 @@ async def on_invite(bot, message):
         return
     log.info("accepting invite to %s from %s", channel, message.nick)
     await bot.join(channel)
+    bot.state.set("chanmgmt", f"autojoin:{channel}", message.nick)
+
+
+@event("KICK")
+async def on_kick(bot, message):
+    """Remove autojoin if the bot is kicked from a channel."""
+    if len(message.params) < 2:
+        return
+    kicked = message.params[1]
+    if kicked != bot.nick:
+        return
+    channel = message.target
+    if bot.state.delete("chanmgmt", f"autojoin:{channel}"):
+        log.info("removed autojoin for %s (kicked)", channel)