Art index panel hides the reason and time while its retry waits #80

While a rate-limited art build waits for its retry, the art index panel on /admin/catalog reads plain "Queued.", with no reason and no time.

• The build's run is already recorded failed with the client's message, and its job is scheduled (Catalog::RateLimitRetry, PR fix(mtg): never wait longer than 30 seconds for a Retry-After #76). MTG::Art::Operation#state falls through to :queued, whose summary is "Queued." and whose facts are empty.
• The wait can be up to an hour, during which the reason and the retry time are invisible.
• The refresh shows both in the same situation: "Queued to retry. The last run failed while downloading: …" with a "Retrying at" fact (Catalog::RefreshOperation, spec 015 AC-3.7). Catalog::Operation::Queue#retry_at already answers the time.

Outcome. The art index panel says the build is queued to retry, why the last one failed, and when the retry is due, as the refresh's panel does.

Found in both reviews of PR #76 by reading the code, and pinned by spec/models/mtg/art/operation_spec.rb (the panel reads "Queued." while the retry waits).