feat: add IRCv3 cap negotiation, channel management, state persistence

Implement CAP LS 302 flow with configurable ircv3_caps list, replacing
the minimal SASL-only registration. Parse IRCv3 message tags (@key=value)
with proper value unescaping. Add channel management plugin (kick, ban,
unban, topic, mode) and bot API methods. Add SQLite key-value StateStore
for plugin state persistence with !state inspection command.

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

plugins/core.py

@@ -163,3 +163,57 @@ async def cmd_admins(bot, message):
     else:
         parts.append("Opers: (none)")
     await bot.reply(message, " | ".join(parts))
+
+
+@command("state", help="Inspect plugin state: !state <list|get|del|clear> ...", admin=True)
+async def cmd_state(bot, message):
+    """Manage the plugin state store.
+
+    Usage:
+        !state list <plugin>          List keys
+        !state get <plugin> <key>     Get a value
+        !state del <plugin> <key>     Delete a key
+        !state clear <plugin>         Clear all state
+    """
+    parts = message.text.split()
+    if len(parts) < 3:
+        await bot.reply(message, "Usage: !state <list|get|del|clear> <plugin> [key]")
+        return
+
+    action = parts[1].lower()
+    plugin = parts[2]
+
+    if action == "list":
+        keys = bot.state.keys(plugin)
+        if keys:
+            await bot.reply(message, f"{plugin}: {', '.join(keys)}")
+        else:
+            await bot.reply(message, f"{plugin}: (no keys)")
+
+    elif action == "get":
+        if len(parts) < 4:
+            await bot.reply(message, "Usage: !state get <plugin> <key>")
+            return
+        key = parts[3]
+        value = bot.state.get(plugin, key)
+        if value is not None:
+            await bot.reply(message, f"{plugin}.{key} = {value}")
+        else:
+            await bot.reply(message, f"{plugin}.{key}: not set")
+
+    elif action == "del":
+        if len(parts) < 4:
+            await bot.reply(message, "Usage: !state del <plugin> <key>")
+            return
+        key = parts[3]
+        if bot.state.delete(plugin, key):
+            await bot.reply(message, f"Deleted {plugin}.{key}")
+        else:
+            await bot.reply(message, f"{plugin}.{key}: not found")
+
+    elif action == "clear":
+        count = bot.state.clear(plugin)
+        await bot.reply(message, f"Cleared {count} key(s) from {plugin}")
+
+    else:
+        await bot.reply(message, "Usage: !state <list|get|del|clear> <plugin> [key]")