Count kind-0 created_at toward modified when it composes via alsoKnownAs

Address Copilot review on #39: a kind-0 event can contribute alsoKnownAs with
no profile fields, so gating the kind-0 created_at on doc.profile alone could
understate modified. Gate on (doc.profile || doc.alsoKnownAs).

Author: melvincarvalho

src/diddoc.js

@@ -96,7 +96,8 @@ export function buildDidDocument(pubkey, { profile, follows, relays } = {}) {
   // into the document, serialized ISO-8601. Representation-only changes are not
   // reflected here (those are conveyed by ETag / Last-Modified).
   const stamps = [
-    doc.profile && profile?.created_at,
+    // kind-0 composes the doc via profile and/or alsoKnownAs
+    (doc.profile || doc.alsoKnownAs) && profile?.created_at,
     doc.follows && follows?.created_at,
     doc.service && relays?.created_at,
   ].filter(Number.isSafeInteger);

test/diddoc.test.js

@@ -48,6 +48,15 @@ test('follows is bounded; the full signed list stays in the kind-3 event', () =>
   assert.equal(d.follows.length, 500);
 });
 
+test('alsoKnownAs-only kind-0 still contributes its created_at to modified', () => {
+  const d = buildDidDocument(PK, {
+    profile: { content: JSON.stringify({ alsoKnownAs: ['https://x.example/#me'] }), created_at: 300 },
+  });
+  assert.equal(d.profile, undefined); // no profile fields composed
+  assert.deepEqual(d.alsoKnownAs, ['https://x.example/#me']);
+  assert.equal(d.modified, '1970-01-01T00:05:00Z'); // kind-0 created_at (300) still counts
+});
+
 test('out-of-range created_at does not throw and is omitted (no modified)', () => {
   const d = buildDidDocument(PK, {
     profile: { content: JSON.stringify({ name: 'X' }), created_at: 1e308 },