fix(post card): clarify full error copying

src/lib/utils/__tests__/error-utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { formatErrorForDisplay } from '../error-utils';
+import { formatErrorForDisplay, serializeErrorForClipboard } from '../error-utils';
 
 describe('error utils', () => {
   it('returns plain string errors unchanged', () => {
@@ -29,4 +29,55 @@ describe('error utils', () => {
       }),
     ).toBe('publish failed: provider: plebpubsub; reason: timeout');
   });
+
+  it('formats nested Error details without dropping the nested message', () => {
+    expect(
+      formatErrorForDisplay({
+        details: {
+          reason: new Error('provider timeout'),
+        },
+        message: 'publish failed',
+      }),
+    ).toBe('publish failed: reason: provider timeout');
+  });
+
+  it('formats cyclic errors without recursing forever', () => {
+    const error = Object.assign(new Error('publish failed'), {
+      details: {
+        elapsedMs: BigInt(5000),
+      },
+    });
+    Object.assign(error.details, { self: error.details });
+
+    expect(formatErrorForDisplay(error)).toBe('publish failed: elapsedMs: 5000; self: [Circular]');
+  });
+
+  it('serializes cyclic errors as valid JSON for copying', () => {
+    const cause = new Error('provider timeout');
+    const error = Object.assign(new Error('publish failed'), {
+      attempts: [{ elapsedMs: BigInt(5000), provider: 'pubsub', reason: cause }],
+    });
+    Object.assign(error, { self: error });
+
+    expect(JSON.parse(serializeErrorForClipboard(error))).toMatchObject({
+      attempts: [
+        {
+          elapsedMs: '5000',
+          provider: 'pubsub',
+          reason: {
+            message: 'provider timeout',
+            name: 'Error',
+          },
+        },
+      ],
+      message: 'publish failed',
+      name: 'Error',
+      self: '[Circular]',
+    });
+  });
+
+  it('keeps string errors unchanged and empty objects as JSON', () => {
+    expect(serializeErrorForClipboard('plain failure')).toBe('plain failure');
+    expect(serializeErrorForClipboard({})).toBe('{}');
+  });
 });