feat: initial implementation

Asyncio IRC bot with decorator-based plugin system.
Zero external dependencies, Python 3.11+.

- IRC protocol: message parsing, formatting, async TCP/TLS connection
- Plugin system: @command and @event decorators, file-based loading
- Bot orchestrator: connect, dispatch, reconnect, nick recovery
- CLI: argparse entry point with TOML config
- Built-in plugins: ping, help, version, echo
- 28 unit tests for parser and plugin system

plugins/example.py

@@ -0,0 +1,23 @@
+"""Example plugin demonstrating the derp plugin API."""
+
+from derp.plugin import command, event
+
+
+@command("echo", help="Echo back text")
+async def cmd_echo(bot, message):
+    """Repeat everything after the command.
+
+    Usage: !echo <text>
+    """
+    parts = message.text.split(None, 1)
+    if len(parts) > 1:
+        await bot.reply(message, parts[1])
+    else:
+        await bot.reply(message, "Usage: !echo <text>")
+
+
+@event("JOIN")
+async def on_join(bot, message):
+    """Greet users joining a channel (skip self)."""
+    if message.nick and message.nick != bot.nick:
+        await bot.send(message.target, f"Hey {message.nick}")