feat(messaging-ui): attachments in inbox mail — reply + compose upload

InboxAdapter gains uploadAttachment + attachment params on mailReply/
composeInternal/composeExternal. MailReader reply and ComposeModal grow an
attach affordance (paperclip + pending chips); mail history renders sent
attachments. MockInboxAdapter implements upload. 67 tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/iios-messaging-ui/src/inbox/hooks.ts

@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useState } from 'react';
 import { useInboxAdapter } from './provider';
-import type { InboxItem, InboxState, MailMessage, MailPerson } from './types';
+import type { InboxItem, InboxState, MailAttachment, MailMessage, MailPerson } from './types';
 
 export interface InboxData {
   items: InboxItem[];
@@ -57,7 +57,9 @@ export interface MailThreadState {
   messages: MailMessage[];
   loading: boolean;
   error: string | null;
-  reply: (content: string) => Promise<void>;
+  reply: (content: string, attachment?: MailAttachment) => Promise<void>;
+  canAttach: boolean;
+  upload: (file: File) => Promise<MailAttachment>;
   refetch: () => void;
 }
 
@@ -97,22 +99,31 @@ export function useMailThread(threadId: string | null): MailThreadState {
 
   const refetch = useCallback(() => setNonce((n) => n + 1), []);
   const reply = useCallback(
-    async (content: string) => {
+    async (content: string, attachment?: MailAttachment) => {
       if (!threadId) return;
-      await adapter.mailReply(threadId, content);
+      await adapter.mailReply(threadId, content, attachment);
       setNonce((n) => n + 1);
     },
     [adapter, threadId],
   );
+  const upload = useCallback(
+    async (file: File) => {
+      if (!adapter.uploadAttachment) throw new Error('attachments are not supported by this adapter');
+      return adapter.uploadAttachment(file);
+    },
+    [adapter],
+  );
 
-  return { messages, loading, error, reply, refetch };
+  return { messages, loading, error, reply, canAttach: typeof adapter.uploadAttachment === 'function', upload, refetch };
 }
 
 export interface ComposeState {
   supported: boolean;
   directory: MailPerson[];
-  sendInternal: (recipientUserId: string, subject: string, text: string) => Promise<void>;
-  sendExternal: (target: string, subject: string, text: string) => Promise<void>;
+  sendInternal: (recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]) => Promise<void>;
+  sendExternal: (target: string, subject: string, text: string, attachments?: MailAttachment[]) => Promise<void>;
+  canAttach: boolean;
+  upload: (file: File) => Promise<MailAttachment>;
 }
 
 /** Compose a new message — in-app (to a person) or external (to an email). */
@@ -138,19 +149,26 @@ export function useCompose(): ComposeState {
   }, [adapter]);
 
   const sendInternal = useCallback(
-    async (recipientUserId: string, subject: string, text: string) => {
+    async (recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]) => {
       if (!adapter.composeInternal) throw new Error('compose is not supported by this adapter');
-      await adapter.composeInternal(recipientUserId, subject, text);
+      await adapter.composeInternal(recipientUserId, subject, text, attachments);
     },
     [adapter],
   );
   const sendExternal = useCallback(
-    async (target: string, subject: string, text: string) => {
+    async (target: string, subject: string, text: string, attachments?: MailAttachment[]) => {
       if (!adapter.composeExternal) throw new Error('compose is not supported by this adapter');
-      await adapter.composeExternal(target, subject, text);
+      await adapter.composeExternal(target, subject, text, attachments);
+    },
+    [adapter],
+  );
+  const upload = useCallback(
+    async (file: File) => {
+      if (!adapter.uploadAttachment) throw new Error('attachments are not supported by this adapter');
+      return adapter.uploadAttachment(file);
     },
     [adapter],
   );
 
-  return { supported, directory, sendInternal, sendExternal };
+  return { supported, directory, sendInternal, sendExternal, canAttach: typeof adapter.uploadAttachment === 'function', upload };
 }