Plain Plug mount, dispatch, and notification bridge for AshUi resources.
Configure with resources: [MyPage] or domains: [MyDomain]. Resources are
matched using their route/2 declaration.
:session_id may be a one-argument function or an MFA whose first argument
is the connection. A binary result is used instead of the bridge cookie; a
nil result falls back to the default cookie-backed identity.
Generated bridge URLs use conn.script_name so forwarded mounts work. Set
:base_path to override that generated prefix.