/* ===== page-shell v1: foldable sections · side outline · vertical/horizontal layout =====
   Needs these tokens on :root (both themes): --bg --surface --surface-2 --ink --ink-2 --muted --rule --accent --accent-soft --f-mono */
.ps-toolbar { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; }
.ps-btn { display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--rule); background: var(--surface); color: var(--ink-2); border-radius: 8px; padding: 6px 10px; font: inherit; font-size: 13px; cursor: pointer; }
.ps-btn:hover { color: var(--ink); border-color: var(--muted); }
.ps-btn svg, .ps-seg svg { width: 14px; height: 14px; flex: none; }
.ps-seg { display: inline-flex; background: var(--surface-2); border-radius: 8px; padding: 3px; gap: 2px; }
.ps-seg button { display: inline-flex; align-items: center; gap: 6px; border: 0; background: transparent; padding: 5px 10px; border-radius: 6px; font: inherit; font-size: 13px; color: var(--ink-2); cursor: pointer; }
.ps-seg button[aria-pressed="true"] { background: var(--surface); color: var(--ink); font-weight: 600; box-shadow: 0 1px 2px rgba(0, 0, 0, .1); }
.ps-step { display: none; gap: 4px; }
body.ps-h .ps-step { display: inline-flex; }
.ps-btn:focus-visible, .ps-seg button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* fold */
.ps-head { display: flex; align-items: center; gap: 10px; min-width: 0; }
.ps-fold { all: unset; box-sizing: border-box; display: flex; align-items: center; gap: 10px; min-width: 0; flex: 1 1 auto; cursor: pointer; border-radius: 6px; }
.ps-fold:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }
.ps-chev { flex: none; width: 16px; height: 16px; color: var(--muted); transition: transform .15s ease; }
.ps-fold:hover .ps-chev { color: var(--ink); }
.is-folded > .ps-head .ps-chev { transform: rotate(-90deg); }
@media (prefers-reduced-motion: reduce) { .ps-chev { transition: none; } }

/* outline */
.ps-outline { max-height: 44vh; overflow-y: auto; scrollbar-width: thin; margin-inline: -8px; }
.ps-outline ol { list-style: none; margin: 0; padding: 0; }
.ps-outline a { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; padding: 4px 8px; border-radius: 6px; color: var(--ink-2); text-decoration: none; font-size: 13px; line-height: 1.35; }
.ps-outline a:hover { background: var(--surface-2); color: var(--ink); }
.ps-outline .n { flex: none; font: 11px/1.4 var(--f-mono); color: var(--muted); font-variant-numeric: tabular-nums; }
.ps-outline li.is-active > a { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.ps-outline li.is-folded > a .t::after { content: " (folded)"; color: var(--muted); font-weight: 400; font-size: 11px; }
.ps-outline ol ol { margin: 2px 0 6px 16px; padding-left: 4px; border-left: 1px solid var(--rule); }
.ps-outline ol ol a { font-size: 12.5px; padding-block: 2px; }
.ps-outline[data-subs="active"] li:not(.is-active) > ol { display: none; }
.ps-none { margin: 0; color: var(--muted); font-size: 13px; }

/* orientation */
.ps-main { position: relative; min-width: 0; }
.ps-main[data-orient="horizontal"] { display: flex; flex-direction: row; align-items: stretch; gap: 20px; overflow-x: auto; overflow-y: hidden; overscroll-behavior-x: contain; scroll-snap-type: x proximity; height: calc(100dvh - 16px); padding-bottom: 10px; scrollbar-width: thin; }
.ps-main[data-orient="horizontal"] > * { flex: 0 0 var(--ps-pane, min(440px, 86vw)); min-width: 0; }
.ps-main[data-orient="horizontal"] > .ps-sec { overflow-y: auto; overscroll-behavior-y: contain; scroll-snap-align: start; padding-inline: 2px 12px; border-right: 1px solid var(--rule); scrollbar-width: thin; }
.ps-main[data-orient="horizontal"] > .ps-sec[data-pane="medium"] { --ps-pane: min(760px, 90vw); }
.ps-main[data-orient="horizontal"] > .ps-sec[data-pane="wide"] { --ps-pane: min(1180px, 94vw); }
.ps-main[data-orient="horizontal"] > .ps-sec > .ps-head { position: sticky; top: 0; z-index: 2; background: var(--bg); }
.ps-main[data-orient="horizontal"] > .ps-sec.is-folded { flex-basis: 52px; overflow: hidden; padding-inline: 0; }
.ps-main[data-orient="horizontal"] > .ps-sec.is-folded > .ps-head { writing-mode: vertical-rl; height: 100%; align-items: flex-start; }
.ps-main[data-orient="horizontal"] > .ps-sec.is-folded > .ps-head .ps-extra { display: none; }