fix(thread): show every message of the thread, not just the tapped one

src/lib/__tests__/email-threading.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { computeReplyThreadingHeaders } from '../email-threading';
+import { computeReplyThreadingHeaders, orderThreadEmails } from '../email-threading';
 
 describe('computeReplyThreadingHeaders', () => {
   it('returns undefined when the parent has no msg-id', () => {
@@ -39,3 +39,22 @@ describe('computeReplyThreadingHeaders', () => {
     ).toEqual({ inReplyTo: '<a@host>', references: '<z@host> <a@host>' });
   });
 });
+
+describe('orderThreadEmails', () => {
+  it('follows the server thread order, not the metadata order', () => {
+    const metas = [{ id: 'c' }, { id: 'a' }, { id: 'b' }];
+    expect(orderThreadEmails(['a', 'b', 'c'], metas)).toEqual([
+      { id: 'a' }, { id: 'b' }, { id: 'c' },
+    ]);
+  });
+
+  it('drops ids whose metadata did not come back', () => {
+    expect(orderThreadEmails(['a', 'gone', 'b'], [{ id: 'a' }, { id: 'b' }])).toEqual([
+      { id: 'a' }, { id: 'b' },
+    ]);
+  });
+
+  it('returns empty for an empty thread', () => {
+    expect(orderThreadEmails([], [])).toEqual([]);
+  });
+});

src/lib/email-threading.ts

@@ -49,3 +49,18 @@ export function computeReplyThreadingHeaders(
     references: chain.map((id) => `<${id}>`).join(' '),
   };
 }
+
+/**
+ * Order thread members for display: JMAP's `Thread.emailIds` is the server's
+ * oldest-first ordering (RFC 8621 §3), so follow it and drop ids whose
+ * metadata didn't come back (expunged between Thread/get and Email/get).
+ */
+export function orderThreadEmails<T extends { id: string }>(
+  emailIds: string[],
+  metas: T[],
+): T[] {
+  const byId = new Map(metas.map((m) => [m.id, m]));
+  return emailIds
+    .map((id) => byId.get(id))
+    .filter((m): m is T => !!m);
+}