/* ============================================================
   layout.css — Structural Layout Only
   This file defines ONLY the layout grid: sidebar, topbar,
   and main panel positions and dimensions.

   RULE: No colours, typography, or component styles here.
         Panel CSS files must NOT override layout. All sizing
         is driven by token variables from tokens.css.
   ============================================================ */

/* ── Global reset ─────────────────────────────────────────── */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  height: 100%;
  overflow: hidden;             /* No page scroll — panels scroll internally */
  background: var(--color-bg);
  color: var(--color-data);
  font-family: var(--font-ui);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  -webkit-font-smoothing: antialiased;
}

/* ── App shell grid ───────────────────────────────────────── */
body {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  grid-template-rows: var(--topbar-h) 1fr;
  grid-template-areas:
    "sidebar topbar"
    "sidebar main";
}

/* ── Sidebar ──────────────────────────────────────────────── */
#sidebar {
  grid-area: sidebar;
  position: fixed;              /* Stays put while main scrolls */
  top: 0;
  left: 0;
  width: var(--sidebar-w);
  height: 100vh;
  z-index: var(--z-sidebar);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ── Topbar ───────────────────────────────────────────────── */
#topbar {
  grid-area: topbar;
  position: fixed;
  top: 0;
  left: var(--sidebar-w);
  right: 0;
  height: var(--topbar-h);
  z-index: var(--z-topbar);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-3);
}

/* ── Main panel ───────────────────────────────────────────── */
#main-panel {
  grid-area: main;
  margin-left: var(--sidebar-w);
  margin-top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  overflow-x: hidden;
  padding: var(--space-4);
}

/* ── Nav list structure ───────────────────────────────────── */
#nav-list {
  list-style: none;
  flex: 1;
  padding: var(--space-1) 0;
  overflow-y: auto;
}

#nav-list li {
  display: block;
}

/* ── Panel loading placeholder ────────────────────────────── */
#panel-loading {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  height: 100%;
  min-height: 200px;
}

/* ── Scrollbar styling ────────────────────────────────────── */
#main-panel::-webkit-scrollbar {
  width: 4px;
}
#main-panel::-webkit-scrollbar-track {
  background: transparent;
}
#main-panel::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: 2px;
}