fix(examples): one malformed example must not take the gallery down

Typing anything into the /examples search box threw "Cannot read
properties of undefined (reading 'map')" and blanked the page. The
haystack the search matches against is built from
`example.components.map(...)`, and `components` was undefined on 27
examples.

`components` is required by `ExampleProject`, so this reads as
impossible — but the gallery is assembled from overlay example modules
whose factories end in `as unknown as ExampleProject`, and the compiler
stops checking there. The field is a promise the type makes and cannot
keep, so the three places that read it now cope with its absence.

CircuitPreview is the one that matters most: it renders as the fallback
whenever an example's thumbnail 404s, so it meets exactly the examples
nobody has generated art for yet.

frontend/src/components/examples/CircuitPreview.tsx

@@ -274,17 +274,22 @@ export const CircuitPreview: React.FC<CircuitPreviewProps> = ({
     const boardKind = example.boardType ?? (isBoardless ? null : 'arduino-uno');
     const boardDef = boardKind ? BOARD_DEFS[boardKind] : undefined;
 
+    // Same defensive read as the gallery's search haystack: overlay example
+    // factories cast their result, so a missing `components` reaches here as
+    // undefined and this preview is exactly where it lands — it renders as the
+    // fallback whenever an example's thumbnail 404s.
+    const components = example.components ?? [];
+
     // Check if the board is explicitly listed in components[]
-    const boardInComponents = example.components.some((c) => isBoardType(c.type));
+    const boardInComponents = components.some((c) => isBoardType(c.type));
 
     if (boardDef && !boardInComponents && !isBoardless) {
       // Board is implicit (pico, esp32, nano examples) — inject at default position
       // Position it to the left of the other components
-      const minCompX =
-        example.components.length > 0 ? Math.min(...example.components.map((c) => c.x)) : 400;
+      const minCompX = components.length > 0 ? Math.min(...components.map((c) => c.x)) : 400;
       const avgCompY =
-        example.components.length > 0
-          ? example.components.reduce((s, c) => s + c.y, 0) / example.components.length
+        components.length > 0
+          ? components.reduce((s, c) => s + c.y, 0) / components.length
           : 150;
       const boardX = Math.max(40, minCompX - boardDef.w - 60);
       const boardY = Math.max(40, avgCompY - boardDef.h / 2);
@@ -292,7 +297,7 @@ export const CircuitPreview: React.FC<CircuitPreviewProps> = ({
     }
 
     // Add all components from the example
-    example.components.forEach((c) => {
+    components.forEach((c) => {
       // For board components that ARE in components[], use the board SVG def
       const def =
         isBoardType(c.type) && boardDef ? boardDef : getCompDef(c.type, c.properties ?? {});

frontend/src/components/examples/ExamplesGallery.tsx

@@ -133,7 +133,12 @@ export const ExamplesGallery: React.FC<ExamplesGalleryProps> = ({ onLoadExample
       example.difficulty,
       getBoardFilter(example),
       ...(example.tags ?? []),
-      ...example.components.map((c) => c.type),
+      // Defensive. `components` is required by ExampleProject, but overlay
+      // example sets are built by factories that cast their result, so the
+      // compiler is not actually guarding this. One entry that omitted it took
+      // the entire gallery down with a TypeError the first time anyone typed in
+      // the search box — a whole page lost to one malformed example.
+      ...(example.components ?? []).map((c) => c.type),
     ]
       .join(' ')
       .toLowerCase();

frontend/src/pages/ExampleDetailPage.tsx

@@ -300,7 +300,7 @@ export const ExampleDetailPage: React.FC = () => {
                 }}
               >
                 <span style={{ color: '#4fc3f7', fontWeight: 700 }}>✓</span>
-                {example.components.length > 0
+                {(example.components?.length ?? 0) > 0
                   ? `${example.components.length} interactive component${example.components.length > 1 ? 's' : ''} on the canvas`
                   : 'Interactive simulation canvas'}
               </li>