/* ============================================================================
   TUTOR production shell (Core 3) - top bar, contextual sub-nav, right rail,
   avatar menu, Ask-TUTOR fab. Structural only; tokens come from tutor-ds-core3.css.
   ========================================================================== */
.shell-bar{display:flex;align-items:center;gap:14px;padding:10px 18px;background:var(--surface);
  border-bottom:1px solid var(--hair);position:sticky;top:0;z-index:60}
.shell-burger{font-size:20px;color:var(--ink);cursor:pointer;background:none;border:none;padding:6px;font-family:inherit}
.shell-brand{font-family:var(--font-display);font-weight:700;font-size:20px;color:var(--ink);text-decoration:none;letter-spacing:-.01em}
.shell-brand span{color:var(--primary-text)}
.shell-search{flex:0 1 300px;display:flex;align-items:center;gap:8px;background:var(--inner);
  border:1px solid var(--hair);border-radius:var(--r-pill);padding:0 14px;min-height:38px}
.shell-search i{color:var(--faint);font-size:15px}
.shell-search input{flex:1;border:none;background:none;outline:none;color:var(--ink);
  font-family:var(--font-ui);font-size:13px;min-width:0}
.shell-search input::placeholder{color:var(--faint)}
.shell-tabs{display:flex;gap:8px;margin:0 auto}
.shell-tab{width:46px;height:40px;display:flex;align-items:center;justify-content:center;
  border-radius:12px;color:var(--muted);font-size:21px;cursor:pointer;position:relative;text-decoration:none}
.shell-tab:hover{background:var(--hover)}
.shell-tab.on{color:var(--primary-text);background:var(--primary-wash)}
.shell-tab.on:after{content:'';position:absolute;bottom:-11px;left:10px;right:10px;height:2.5px;
  background:var(--primary);border-radius:2px}
.shell-right{display:flex;align-items:center;gap:12px}
.shell-bell{position:relative;background:none;border:none;color:var(--muted);font-size:19px;cursor:pointer;padding:6px;font-family:inherit}
.shell-bell .nb{position:absolute;top:2px;right:0;background:var(--err);color:#fff;font-size:9.5px;
  font-weight:700;border-radius:999px;padding:1px 5px;display:none}
.shell-avatar{width:34px;height:34px;border-radius:50%;background:var(--primary);color:#fff;
  display:inline-flex;align-items:center;justify-content:center;font-size:13px;font-weight:600;
  cursor:pointer;border:none;font-family:inherit}
.shell-menu,.shell-notif{position:absolute;top:52px;right:14px;background:var(--surface);
  border:1px solid var(--hair);border-radius:14px;box-shadow:var(--shadow-lg);width:250px;
  overflow:hidden;display:none;z-index:70}
.shell-menu.open,.shell-notif.open{display:block}
.shell-menu .mh{display:flex;align-items:center;gap:10px;padding:13px 15px;border-bottom:1px solid var(--hair)}
.shell-mi{display:flex;align-items:center;gap:11px;padding:10px 15px;font-size:13.5px;color:var(--ink);
  cursor:pointer;text-decoration:none;background:none;border:none;width:100%;text-align:left;font-family:inherit}
.shell-mi i{font-size:16px;color:var(--muted);width:18px;text-align:center}
.shell-mi:hover{background:var(--hover)}
.shell-notif{width:300px;max-height:55vh;overflow-y:auto;padding:12px 14px}
.shell-notif .nt{padding:8px 0;border-bottom:1px solid var(--hair);font-size:12.5px;color:var(--muted)}
.shell-notif .nt b{color:var(--ink);display:block}
.shell-notif .nt:last-child{border-bottom:none}

.shell-layout{display:grid;grid-template-columns:208px minmax(0,1fr) 252px;gap:0;
  max-width:1240px;margin:0 auto;min-height:calc(100vh - 61px)}
.shell-subnav{border-right:1px solid var(--hair);background:var(--surface);padding:14px 10px;
  position:sticky;top:61px;align-self:start;max-height:calc(100vh - 61px);overflow-y:auto;overflow-x:hidden}
.sn-head{display:flex;align-items:center;justify-content:space-between;font-size:11px;font-weight:700;
  letter-spacing:.1em;color:var(--faint);padding:2px 10px 10px}
.sn-item{display:flex;align-items:center;gap:10px;padding:9px 12px;border-radius:10px;font-size:13.5px;
  font-weight:500;color:var(--ink);cursor:pointer;border:none;background:none;width:100%;
  text-align:left;font-family:inherit}
.sn-item i{font-size:17px;color:var(--muted);width:18px;text-align:center}
.sn-item.on{background:var(--primary-wash);color:var(--primary-ink);font-weight:600}
.sn-item.on i{color:var(--primary-ink)}
.sn-item:not(.on):hover{background:var(--hover)}
.sn-sep{height:1px;background:var(--hair);margin:10px 8px}
.shell-main{padding:22px 24px;min-width:0}
.shell-rail{border-left:1px solid var(--hair);background:var(--surface);padding:16px 14px;
  display:flex;flex-direction:column;gap:12px;position:sticky;top:61px;align-self:start}
.rc{background:var(--inner);border:1px solid var(--hair);border-radius:var(--r);padding:13px 14px}
.rc h4{font-size:12px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);
  margin:0 0 8px;display:flex;justify-content:space-between;font-family:var(--font-ui)}
.rc p{font-size:12.5px;color:var(--muted);margin:0;line-height:1.5}
.shell-fab{position:fixed;bottom:20px;right:20px;width:52px;height:52px;border-radius:50%;
  background:var(--primary);color:#fff;display:flex;align-items:center;justify-content:center;
  font-size:23px;box-shadow:var(--shadow-lg);text-decoration:none;z-index:50;
  transition:transform var(--dur-fast) var(--ease)}
.shell-fab:hover{transform:translateY(-2px)}

[data-tier="early"] .sn-item{font-size:16px;min-height:52px}
[data-tier="early"] .shell-fab{width:64px;height:64px;font-size:28px}
@media(max-width:960px){
  .shell-layout{grid-template-columns:1fr}
  .shell-rail{display:none}
  .shell-subnav{display:none;position:fixed;left:0;top:61px;bottom:0;width:240px;z-index:65;box-shadow:var(--shadow-lg)}
  .shell-subnav.open{display:block}
  .shell-search{display:none}
}

/* Subnav close (X): only meaningful on mobile where the subnav is a drawer.
   On desktop the panel is persistent, so hide the X to avoid a dead button. */
.sn-head .ti-x{display:none}
@media(max-width:960px){ .sn-head .ti-x{display:inline-block} }