webui: one settings snapshot and a names read that rethrows a refusal (row 167, #1664)

The Settings page held the launch settings twice, one copy for the launch form and the
token-limit reset and one for the Assistant section. A save in one form left the other with
the old revision, so its next save was refused with revision-conflict. Now one snapshot
serves both. Every successful save or reset sets it from the answer, a read replaces it only
while no form has a draft, and reload clears it.

The names read now rethrows a 403 or signed-out like the usage, instances and limits reads,
so a refusal gives the refused page instead of an empty name field.

Tests: the names refusal, one per snapshot path (launch save, assistant save, reset), and a
null body on /api/name and /api/assistant-stop. limits-browser.test.mjs:54 now expects the
reset's revision on the following save.