The CLI accepts any URL as default parameter, and is smart about how it loads them. Before #9018, this always resulted in one or more recordings being created (via a stream of LogMsg). #9018 introduced a separate pipeline that special-case redap catalog urls, which are now bypassing the aforementioned pipeline and directly handled by the redap browser crate. Several hacks are involved on the way. This should be cleaned up as follows.

1. The URL_OR_PATHS arg of the rerun cli should only accept recording-like stuff. That should exclude catalog URL, because these are not recording-like (for now). Passing a /catalog url there should immediately trigger an error.
2. Introduce alternative ways to add/keep Redap servers to the viewer
   • Once added, servers should remain in the list and persisted across viewer relaunch (until explicitly removed)
   • The UI should have a way to add a server with a + button.
   • The CLI could have a --add-server (or some other name) option to explicitly add a redap server to the list.

Implementation-wise, early-erroring on non-recording grpc url should allow us to have a type-level guarantee that a rerun:// url corresponds to a recording (e.g. a RedapRecordingAddress type), which should allow cleanup up the various hacks recently introduced.