Initial implementation of xtrm-agent multi-agent system

Multi-agent AI automation system with shared message bus, specialized
roles (coder/researcher/reviewer), and deny-by-default security.

- Config system with Pydantic validation and YAML loading
- Async message bus with inter-agent delegation
- LLM providers: Anthropic (Claude) and LiteLLM (DeepSeek/Kimi/MiniMax)
- Tool system: registry, builtins (file/bash/web), approval engine, MCP client
- Agent engine with tool-calling loop and orchestrator for multi-agent management
- CLI channel (REPL) and Discord channel
- Docker + Dockge deployment config
- Typer CLI: chat, serve, status, agents commands

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

xtrm_agent/router.py

@@ -0,0 +1,48 @@
+"""Message router — routes inbound messages to the correct agent."""
+
+from __future__ import annotations
+
+import re
+
+from xtrm_agent.bus import InboundMessage
+
+
+class Router:
+    """Routes messages to agents based on mentions, channel defaults, or delegation."""
+
+    def __init__(
+        self,
+        agent_names: list[str],
+        channel_defaults: dict[str, str] | None = None,
+    ) -> None:
+        self.agent_names = set(agent_names)
+        self.channel_defaults = channel_defaults or {}
+
+    def resolve(self, msg: InboundMessage) -> str:
+        """Determine which agent should handle this message."""
+        # 1. Explicit target set by delegation or system
+        if msg.target_agent and msg.target_agent in self.agent_names:
+            return msg.target_agent
+
+        # 2. @agent_name mention in content
+        mentioned = self._extract_mention(msg.content)
+        if mentioned and mentioned in self.agent_names:
+            return mentioned
+
+        # 3. Channel default
+        default = self.channel_defaults.get(msg.channel)
+        if default and default in self.agent_names:
+            return default
+
+        # 4. First available agent
+        return next(iter(self.agent_names)) if self.agent_names else "coder"
+
+    def strip_mention(self, content: str) -> str:
+        """Remove @agent_name from content."""
+        return re.sub(r"@(\w+)\s*", "", content, count=1).strip()
+
+    def _extract_mention(self, content: str) -> str | None:
+        match = re.match(r"@(\w+)", content.strip())
+        if match:
+            return match.group(1).lower()
+        return None