Bulk Request Error Handling with ApiRequest

Reached a point in the minimal interface where I needed to claim multiple samples at once. Each operation could fail independently, but I have no way to agglomerate error messages back to the user due to the way ApiRequest is dumping us to error pages.

I suspect we need a slightly more general mechanism for request errors and to take more care what routes return a json response and what routes return html pages, as any routes that can return both under different circumstances make javascript and python parsing of errors very difficult.

Start by tracing ApiRequest and the minimal interface's bulk sample-claim path. Map which routes currently return JSON versus HTML, including independently failing operations, and identify how JavaScript and Python callers receive errors. Done means the request-error mechanism and route response behavior are defined well enough to aggregate failures without forcing clients to parse error pages.

Written by the indexing model from the issue text.