fix(picker): variant-true previews + datasheet popover above the modal

- The card preview creates the live element but only forwarded
  defaultValues.value, so variants sharing a tag rendered identically (both
  M5Stack Chain matrices showed the dark RGB housing — the mono flag never
  reached the element). Forward every defaultValues entry, matching what
  DynamicComponent assigns at placement.
- The hover datasheet panel sat at z-index 2000 while the picker overlay was
  raised to 9000 (above the AI chat), hiding the popover behind the very
  modal that summons it. Raise it to 9100.

frontend/src/components/ComponentPickerModal.css

@@ -485,7 +485,9 @@
  * ------------------------------------------------------------------ */
 .component-info-panel {
   position: fixed;
-  z-index: 2000;
+  /* Above the picker overlay (9000) — the popover is summoned by hovering
+     cards INSIDE that modal, so anything lower hides it behind the list. */
+  z-index: 9100;
   width: 316px;
   max-height: 74vh;
   overflow-y: auto;

frontend/src/components/ComponentPickerModal.tsx

@@ -576,10 +576,17 @@ const ComponentCard: React.FC<ComponentCardProps> = ({ component, onSelect, hove
     (element as HTMLElement).style.transform = `scale(${scale})`;
     (element as HTMLElement).style.transformOrigin = 'center center';
 
-    // Pass the preset's default value through so value-sensitive elements
-    // (e.g. wokwi-resistor color bands) render the right look in the picker.
-    if (component.defaultValues?.value !== undefined) {
-      (element as any).value = component.defaultValues.value;
+    // Pass the preset's defaults through so variant-sensitive elements render
+    // the right look in the picker — e.g. wokwi-resistor color bands (value)
+    // or the M5Stack Chain matrix light/dark housing (mono). Same property
+    // assignment DynamicComponent performs when the part is placed, so any
+    // element that tolerates placement tolerates the preview.
+    for (const [key, val] of Object.entries(component.defaultValues ?? {})) {
+      try {
+        (element as any)[key] = val;
+      } catch {
+        /* read-only prop on some upstream element — skip */
+      }
     }
 
     // Set default properties for better preview appearance