The chat.js fetch wrapper recorded a request-not-found from /api/requests/<id>/workspace as a missing request and then served a synthetic 404 to the request panel's rereads, failing 11 request-browser tests. Only the request's own read records a miss now. Adds a regression test that fails on 9d3eb9e11, and bounds the r3 held-404 test's check on its refresh reads, which raced Files' cached repaint under load.