feat: one gateway port with path-mounted frontends, markdown chat, collapsible sidebars

src/beaver_gateway/core/registry.py

@@ -84,3 +84,11 @@ class Gateway:
     frontends: list[Frontend] = field(default_factory=list)
     texts: ConversationTexts | None = None
     """Merge prompt and seed bodies for ``core/conversations`` (§8.2-8.3)."""
+    host: str = "0.0.0.0"  # noqa: S104
+    port: int = 8000
+    """The one listener; every HTTP frontend is mounted under its ``path``."""
+    public_url: str | None = None
+    """Origin the reverse proxy shows the world (``https://b.example.com``).
+
+    Advertised endpoints and MCP discovery are built on it; ``None``
+    derives the origin from each request."""