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

docs/USAGE.md

@@ -0,0 +1,97 @@
+# Usage Guide
+
+## Running
+
+```bash
+# From project directory
+derp
+
+# With options
+derp --config /path/to/derp.toml --verbose
+```
+
+## CLI Flags
+
+| Flag | Description |
+|------|-------------|
+| `-c, --config PATH` | Config file path |
+| `-v, --verbose` | Debug logging |
+| `-V, --version` | Print version |
+| `-h, --help` | Show help |
+
+## Configuration
+
+All settings in `config/derp.toml`:
+
+```toml
+[server]
+host = "irc.libera.chat"    # IRC server hostname
+port = 6697                   # Port (6697 = TLS, 6667 = plain)
+tls = true                    # Enable TLS encryption
+nick = "derp"                 # Bot nickname
+user = "derp"                 # Username (ident)
+realname = "derp IRC bot"     # Real name field
+password = ""                 # Server password (optional)
+
+[bot]
+prefix = "!"                  # Command prefix character
+channels = ["#test"]          # Channels to join on connect
+plugins_dir = "plugins"       # Plugin directory path
+
+[logging]
+level = "info"                # Logging level: debug, info, warning, error
+```
+
+## Built-in Commands
+
+| Command | Description |
+|---------|-------------|
+| `!ping` | Bot responds with "pong" |
+| `!help` | List all available commands |
+| `!help <cmd>` | Show help for a specific command |
+| `!version` | Show bot version |
+| `!echo <text>` | Echo back text (example plugin) |
+
+## Writing Plugins
+
+Create a `.py` file in the `plugins/` directory:
+
+```python
+from derp.plugin import command, event
+
+@command("hello", help="Greet the user")
+async def cmd_hello(bot, message):
+    """Handler receives bot instance and parsed Message."""
+    await bot.reply(message, f"Hello, {message.nick}!")
+
+@event("JOIN")
+async def on_join(bot, message):
+    """Event handlers fire on IRC events (JOIN, PART, QUIT, etc.)."""
+    if message.nick != bot.nick:
+        await bot.send(message.target, f"Welcome, {message.nick}")
+```
+
+### Plugin API
+
+The `bot` object provides:
+
+| Method | Description |
+|--------|-------------|
+| `bot.send(target, text)` | Send message to channel or nick |
+| `bot.reply(msg, text)` | Reply to source (channel or PM) |
+| `bot.action(target, text)` | Send `/me` action |
+| `bot.join(channel)` | Join a channel |
+| `bot.part(channel [, reason])` | Leave a channel |
+| `bot.quit([reason])` | Disconnect from server |
+
+The `message` object provides:
+
+| Attribute | Description |
+|-----------|-------------|
+| `message.nick` | Sender's nickname |
+| `message.prefix` | Full `nick!user@host` prefix |
+| `message.command` | IRC command (PRIVMSG, JOIN, etc.) |
+| `message.target` | First param (channel or nick) |
+| `message.text` | Trailing text content |
+| `message.is_channel` | Whether target is a channel |
+| `message.params` | All message parameters |