feat: editor improvements and collapsible sidebars

Add collapse/expand toggle for the AppShell navigation sidebar and the
editor properties panel (both persisted to localStorage). Bundles other
in-progress editor work including position anchors, outlet sizing, PBR
textures, window slope/frame depth, curtain metadata, and various 2D/3D
rendering tweaks.

apps/client/src/components/editor/EditorToolbar.tsx

@@ -53,7 +53,7 @@ export function EditorToolbar({ onSave, isSaving, onExport, onImport }: EditorTo
   const { state, setTool, setZoom, dispatch } = useEditor();
   const { undo, redo, canUndo, canRedo } = useUndoRedo();
 
-  const { activeTool, zoom, gridVisible, snapEnabled, layerVisibility } = state;
+  const { activeTool, zoom, gridVisible, snapEnabled, layerVisibility, globalFurnitureOpacity } = state;
 
   const zoomPercent = Math.round((zoom / 100) * 100);
 
@@ -193,6 +193,37 @@ export function EditorToolbar({ onSave, isSaving, onExport, onImport }: EditorTo
         >
           {t('toolbar.meas')}
         </button>
+        <label
+          title={t('toolbar.furnitureOpacity') ?? 'Furniture opacity'}
+          style={{
+            display: 'flex',
+            alignItems: 'center',
+            gap: 6,
+            paddingLeft: 6,
+            fontSize: 12,
+            color: 'var(--color-text-secondary)',
+          }}
+        >
+          <span aria-hidden style={{ fontSize: 14 }}>◐</span>
+          <input
+            type="range"
+            min={0}
+            max={1}
+            step={0.05}
+            value={globalFurnitureOpacity}
+            onChange={(e) => {
+              const next = parseFloat(e.target.value);
+              if (Number.isFinite(next)) {
+                dispatch({ type: 'SET_GLOBAL_FURNITURE_OPACITY', opacity: next });
+              }
+            }}
+            style={{ width: 70 }}
+            aria-label={t('toolbar.furnitureOpacity') ?? 'Furniture opacity'}
+          />
+          <span style={{ minWidth: 30, textAlign: 'right', fontVariantNumeric: 'tabular-nums' }}>
+            {Math.round(globalFurnitureOpacity * 100)}%
+          </span>
+        </label>
       </div>
 
       {/* Alignment tools — visible when 2+ items selected */}