refactor: split flat core into capability packages, layer the conversations service, English defaults for every model-facing text

src/beaver_gateway/backends/base.py

@@ -1,7 +1,7 @@
 """Backend protocol.
 
 A backend turns an Anthropic-style turn (``messages`` + agent definition)
-into a stream of :class:`~beaver_gateway.core.events.MessageStreamEvent`
+into a stream of :class:`~beaver_gateway.events.stream.MessageStreamEvent`
 records. The frontend serializes whatever comes out straight to SSE, so
 backends are the only place where provider quirks are translated.
 
@@ -12,7 +12,7 @@ subclassing - to keep them swappable in tests with bare async generators.
 ignored by backends that don't keep state: ``conversation_id`` (stable id
 the backend may pin a live session to), ``session_id`` (backend session to
 resume when nothing is live), ``capture`` (a
-:class:`~beaver_gateway.core.turn_capture.TurnCapture` the backend fills
+:class:`~beaver_gateway.backends.capture.TurnCapture` the backend fills
 after the stream closes).
 """
 
@@ -26,7 +26,7 @@ if TYPE_CHECKING:
     from anthropic.types import MessageParam
 
     from beaver_gateway.agents.base import BaseAgent
-    from beaver_gateway.core.events import MessageStreamEvent
+    from beaver_gateway.events.stream import MessageStreamEvent
 
 
 class Backend(Protocol):