The spec review checklist still asked for >= 50%, the figure the gate sat
at before it was found to be unreachable; traceability-ci.md carried 82%
throughout. Both now read 88%, matching the ratchet, and the checklist
points at `bun run traces:coverage` rather than inviting anyone to trust a
number written in a document.
Also refreshes the two stale coverage snapshots in traceability-ci.md
(~86% from July 2026, and targets of 70% and 90% that the current 90%
already passes) and records the 50 -> 82 -> 88 ratchet history.
Add specs for the account menu, downloads-as-offline-library, offline
downloaded-only filter, and scoped search (+ boundary revision). Add the
new UR/DR entries to requirements.md, update ux-flows, and regenerate the
traceability matrix.
TRACES: UR-049, UR-050, UR-052, UR-053, UR-054, UR-055, UR-056
dtourolle