Library page + current design as a selectable version

• Library (library.html) — the first batch of concept articles: the blast radius, the mandate, permission granularity, the permissions bill of materials, framing the SLA, risk acceptance, second- and third-order effects, graphs of graphs, Wardley maps, and open-by-default. Grouped into five themes, each a short read with its infographic; a card index opens a reading overlay with related links and provenance. Infographics are optimised and inlined so they render in every context (the framed pages can't use the vault's image bridge).
• Current design is now its own selectable version. The switcher lists v0.4.2 (current — unified menu + consumption pricing), v0.4.0 (the redesign as first shipped, with its original pricing), and v0.3.0. Going forward, a new minor (e.g. v0.5.0) starts as a copy of the last v0.4.x.
• Two tracks, kept distinct: the switcher lists meaningfully-different design snapshots; the changelog lists releases (a page addition like this one is a release without a new design snapshot, so the switcher's latest stays v0.4.2).