add 'Required' selector, UI/scroll fixes, auth cookie/cache tweaks, and gateway password gating

env-builder: add 'Required' selector, UI/scroll fixes, auth cookie/cache tweaks, and gateway password gating

env-builder.html

@@ -130,6 +130,7 @@ body {
   background: var(--bg2);
   display: flex;
   flex-direction: column;
+  min-height: 0;
   overflow: hidden;
 }
 
@@ -577,6 +578,7 @@ body {
 .panel-scroll {
   flex: 1;
   overflow-y: auto;
+  min-height: 0;
   padding: 16px;
   display: flex;
   flex-direction: column;
@@ -780,8 +782,6 @@ body {
 }
 .tag-legend[open] .legend-hint { opacity: 0; }
 .toolbar-hint { color: var(--muted); font-size: 12px; margin-right: 10px; white-space: nowrap; }
-.quick-guide { margin: 0; padding-left: 18px; color: var(--muted); display: grid; gap: 6px; font-size: 12.5px; }
-.quick-guide strong { color: var(--text); }
 .legend-body {
   padding: 8px 12px 10px;
   border-top: 1px solid var(--border);