/* Session history rail — expands as an overlay on top of the canvas, never
   a push-layout, so it doesn't fight the adjustable divider (two things
   resizing canvas width at once). Per AGENTS.md's shared UX mechanics. */
.rail-toggle{position:absolute;top:12px;left:12px;z-index:15;display:flex;align-items:center;gap:6px;padding:7px 12px;border:1px solid var(--line);border-radius:999px;background:var(--surface-2);color:var(--fg);font-size:13px;font-weight:600;cursor:pointer}
.rail-toggle:hover{border-color:var(--primary)}
.rail-overlay{position:absolute;inset:0;z-index:30;display:none;background:rgba(0,0,0,.45)}
.rail-overlay.open{display:block}
.rail-panel{position:absolute;top:0;left:0;bottom:0;width:280px;max-width:80%;background:var(--surface);border-right:1px solid var(--line);display:flex;flex-direction:column;padding:14px}
.rail-panel-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}
.rail-panel-header strong{font-size:14px}
.rail-close{background:transparent;border:0;color:var(--muted);cursor:pointer;font-size:18px;line-height:1;padding:4px}
.rail-new{padding:9px;border:1px dashed var(--line);border-radius:10px;background:transparent;color:var(--fg);font-size:13px;cursor:pointer;margin-bottom:10px}
.rail-new:hover{border-color:var(--primary);color:var(--primary)}
.rail-list{overflow-y:auto;display:flex;flex-direction:column;gap:6px}
.rail-item{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:9px 10px;border-radius:9px;background:transparent;border:1px solid transparent;cursor:pointer;color:var(--fg);font-size:13px;text-align:left}
.rail-item:hover{background:var(--surface-2)}
.rail-item.active{border-color:var(--primary);background:rgba(212,255,79,.08)}
.rail-item .title{overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.rail-item .del{color:var(--faint);flex-shrink:0}
.rail-item .del:hover{color:var(--accent)}
.rail-empty{color:var(--muted);font-size:13px;padding:12px 4px}