feat: implement channel runtime connectors

app-instance/backend/beaver/interfaces/channels/__init__.py

@@ -1,7 +1,17 @@
 """Channel interfaces."""
 
 from .base import ChannelAdapter
+from .base import ChannelInboundSink
+from .external_connector import ExternalConnectorChannel
 from .manager import ChannelManager
 from .memory import MemoryChannelAdapter
+from .terminal_websocket import TerminalWebSocketAdapter
 
-__all__ = ["ChannelAdapter", "ChannelManager", "MemoryChannelAdapter"]
+__all__ = [
+    "ChannelAdapter",
+    "ChannelInboundSink",
+    "ExternalConnectorChannel",
+    "ChannelManager",
+    "MemoryChannelAdapter",
+    "TerminalWebSocketAdapter",
+]