Submit joins the admission queue first and sends the PAT only once the
reservation is held. Queued state shows the shaping orb, ordinal position
with estimate, and an exit button whose label changes with the wait;
running switches the orb to solving. Rejoin once on a lost reservation or
ticket, best-effort leave on pagehide. Mock server gains the queue
endpoints and five scenarios; contract, unit and e2e tests cover them.
Static frontend with vendored marked/DOMPurify, bounded Markdown
pipeline, same-origin mock server with scenario selection, unit,
contract and CDP end-to-end tests under frontend/**.
