feat(channels): add unified channel framework with Telegram and Discord support

Introduce the new channel unification architecture:
- Core framework: base channel class, bus, consumer, channel manager,
  middleware, mixins, capabilities, formatter, retry, plugin system
- Telegram channel implementation with bot token validation
- Discord channel implementation with bot token validation
- Refactored iMessage to use new base channel architecture
- Updated CLI: /channel commands, serve mode, channel setup wizard
- Updated onboard wizard to support multi-channel selection
- Config settings for all channel types
- Stream events: media attachment support, done event content field
- Comprehensive test coverage for channels, bus, and manager

EvoScientist/channels/bus/events.py

@@ -0,0 +1,52 @@
+"""Event types for the message bus."""
+
+from dataclasses import dataclass, field
+from datetime import datetime
+from typing import Any
+
+
+@dataclass
+class InboundMessage:
+    """Message received from a chat channel.
+
+    Carries enough context for the bus to route and for the agent
+    to build a session: which channel, who sent it, which chat.
+    """
+
+    channel: str
+    sender_id: str
+    chat_id: str
+    content: str
+    timestamp: datetime = field(default_factory=datetime.now)
+    message_id: str = ""
+    media: list[str] = field(default_factory=list)
+    metadata: dict[str, Any] = field(default_factory=dict)
+    is_group: bool = False
+    was_mentioned: bool = True
+
+    @property
+    def sender(self) -> str:
+        """Alias for ``sender_id`` (compatibility with IncomingMessage)."""
+        return self.sender_id
+
+    @property
+    def session_key(self) -> str:
+        """Unique key for session identification: ``channel:chat_id``."""
+        return f"{self.channel}:{self.chat_id}"
+
+
+@dataclass
+class OutboundMessage:
+    """Message to send to a chat channel."""
+
+    channel: str
+    chat_id: str
+    content: str
+    reply_to: str | None = None
+    media: list[str] = field(default_factory=list)
+    metadata: dict[str, Any] = field(default_factory=dict)
+
+    @property
+    def recipient(self) -> str:
+        """Alias for ``chat_id`` (compatibility with OutgoingMessage)."""
+        return self.chat_id