test(sim): Phase 1d-tests A — netlist snapshots for every gallery example

Snapshots the full SPICE netlist for every example across all six
data/examples-*.ts modules (168 examples total):
  analog: 30, digital: 38, 100-days: 49, epaper: 7,
  picow-wifi: 4, circuits: 40.

Pipeline: example → exampleToBuildNetlistInput → buildNetlist →
strip leading timestamp comment → toMatchSnapshot.  Uses the
production helper (same one loadExample.ts uses) so any future
change to the brand-prefix rule / board filter / analysis picker
appears in the snapshot diff automatically.

To regenerate after a legitimate model change:
  npx vitest run -u src/__tests__/examples-netlist-snapshot.test.ts

The PR diff of the snapshot file becomes the evidence of which
circuits change in response.  Reviewer can scan the diff to confirm
the change is intended.

168 new sub-tests bring total to 1640 passing (was 1472).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/__tests__/examples-netlist-snapshot.test.ts

@@ -0,0 +1,80 @@
+/**
+ * Netlist snapshot tests (Phase 1d-tests A).
+ *
+ * For every example across ALL `examples-*.ts` modules, build the
+ * SPICE netlist via the production pipeline and snapshot the FULL
+ * netlist string.  If a refactor changes how `componentToSpice`,
+ * `NetlistBuilder`, or `storeAdapter` emit cards, the diff lands in
+ * `__snapshots__/examples-netlist-snapshot.test.ts.snap` and a
+ * reviewer sees exactly what changed across every example.
+ *
+ * To intentionally update the snapshots after a legitimate model
+ * change:
+ *
+ *   npx vitest run -u src/__tests__/examples-netlist-snapshot.test.ts
+ *
+ * The PR diff of the snapshot file becomes the evidence of which
+ * circuits are affected.
+ *
+ * Test fidelity rule (memory `feedback_tests_import_real_code`):
+ * imports the example arrays directly from the source modules and
+ * uses the same `exampleToBuildNetlistInput` that production
+ * `loadExample.ts` uses.  Nothing is duplicated.
+ */
+import { describe, it, expect } from 'vitest';
+import { analogExamples } from '../data/examples-analog';
+import { digitalExamples } from '../data/examples-digital';
+import { hundredDaysExamples } from '../data/examples-100-days';
+import { epaperExamples } from '../data/examples-displays-epaper';
+import { picowWifiExamples } from '../data/examples-picow-wifi';
+import { circuitExamples } from '../data/examples-circuits';
+import { exampleToBuildNetlistInput } from '../utils/exampleToBuildNetlistInput';
+import { buildNetlist } from '../simulation/spice/NetlistBuilder';
+import type { ExampleProject } from '../data/examples';
+
+/**
+ * Normalise the netlist before snapshotting:
+ *   - strip the leading `* Velxio circuit @ <ISO timestamp>` comment
+ *     (timestamp would flake every run)
+ *
+ * Everything else is verbatim — model lines, source ordering, etc.
+ */
+function snapshotNetlist(netlist: string): string {
+  return netlist.replace(/^\* Velxio circuit @[^\n]*\n/, '* Velxio circuit\n');
+}
+
+function snapshotExample(example: ExampleProject): string {
+  // Some examples have no electrical components (firmware-only).  The
+  // builder still produces a minimal netlist with the analysis card +
+  // `.end`; snapshot that for completeness.
+  const input = exampleToBuildNetlistInput(example);
+  const { netlist } = buildNetlist(input);
+  return snapshotNetlist(netlist);
+}
+
+interface Bucket {
+  name: string;
+  examples: ExampleProject[];
+}
+
+const BUCKETS: Bucket[] = [
+  { name: 'analog', examples: analogExamples },
+  { name: 'digital', examples: digitalExamples },
+  { name: '100-days', examples: hundredDaysExamples },
+  { name: 'epaper', examples: epaperExamples },
+  { name: 'picow-wifi', examples: picowWifiExamples },
+  { name: 'circuits', examples: circuitExamples },
+];
+
+for (const bucket of BUCKETS) {
+  describe(`netlist snapshot — ${bucket.name} (${bucket.examples.length} examples)`, () => {
+    it.each(bucket.examples.map((ex) => [ex.id, ex] as const))(
+      '%s',
+      { timeout: 5_000 },
+      (_id, example) => {
+        const netlist = snapshotExample(example);
+        expect(netlist).toMatchSnapshot();
+      },
+    );
+  });
+}