UX second pass: icon-only header, pane-toggle cue, schema columns, facet cleanup

src/app/components/ChartBuilderModal.module.css

@@ -1007,25 +1007,3 @@
   opacity: 0.5;
   cursor: not-allowed;
 }
-
-/* Reserved faceting placeholder (Phase 4) — non-interactive, signals where it'll live. */
-.facetSlot {
-  display: flex;
-  align-items: center;
-  gap: var(--space-2);
-  min-width: 150px;
-  min-height: var(--control-height);
-  padding: var(--space-1) var(--space-3);
-  border: var(--border-width) dashed var(--border);
-  color: var(--text-placeholder);
-  font-size: 12px;
-  user-select: none;
-}
-
-.facetTag {
-  padding: 0 var(--space-2);
-  border: var(--border-width) solid var(--border);
-  font-size: 10px;
-  text-transform: uppercase;
-  letter-spacing: 0.03em;
-}