test(integration): draft handling and shared-folder moves

Add draft and shared-folder-move coverage (suite now 31 tests). Findings are
asserted server-side or pinned with test.fail where the UI is incomplete.

Drafts (07):
- multiple recipients (committed and typed-but-uncommitted) persist, and the
  draft reopens via the continue-draft button;
- a server-created draft (with $draft) shows the continue-draft button;
- a changed sender identity is saved to the draft on the server;
- KNOWN BUG (test.fail): reopening a draft resets the From selector to the
  default identity instead of the one the draft was saved with.

Shared-folder moves (08):
- shared -> shared (same owner) moves work in both directions (server-verified);
- KNOWN LIMITATION (test.fail): cross-account moves (own account <-> shared
  folder) don't relocate the message — the Move-to submenu offers the target
  but clicking it is a no-op.

Hooks added: composer From select + save-status, viewer edit-draft button,
context-menu "Move to" submenu + per-target testids (testId on
ContextMenuSubMenu). Helpers: JMAP identities/createDraft/sharing, composer
drive + move-via-submenu. README documents the findings.

components/email/email-composer.tsx

@@ -2071,7 +2071,7 @@ export function EmailComposer({
           <Button variant="ghost" size="icon" onClick={handleClose} className="h-9 w-9 md:h-8 md:w-8">
             <X className="w-5 h-5 md:w-4 md:h-4" />
           </Button>
-          <div className="flex items-center gap-2">
+          <div className="flex items-center gap-2" data-testid="composer-save-status" data-status={saveStatus}>
             <h3 className="font-semibold text-base">{t('new_message')}</h3>
             {saveStatus === 'saving' && (
               <div className="flex items-center gap-1 text-xs text-muted-foreground">
@@ -2136,6 +2136,7 @@ export function EmailComposer({
                 <select
                   value={selectedIdentityId || primaryIdentity?.id || ''}
                   onChange={(e) => setSelectedIdentityId(e.target.value)}
+                  data-testid="composer-from"
                   className="flex-1 bg-transparent text-sm text-foreground outline-none cursor-pointer hover:text-muted-foreground transition-colors min-w-0 truncate"
                 >
                   {identityGroups.length > 0

components/email/email-context-menu.tsx

@@ -307,7 +307,7 @@ export function EmailContextMenu({
 
       {/* Move to submenu */}
       {moveTree.length > 0 && (
-        <ContextMenuSubMenu icon={FolderInput} label={t("move_to")}>
+        <ContextMenuSubMenu icon={FolderInput} label={t("move_to")} testId="ctx-move-to">
           {(() => {
             const renderNodes = (nodes: MailboxNode[]) => {
               return nodes.map((node) => {
@@ -320,6 +320,7 @@ export function EmailContextMenu({
                       <ContextMenuItem
                         icon={Icon}
                         label={nodeLabel}
+                        testId={`move-to:${node.id}`}
                         onClick={() =>
                           handleAction(() =>
                             showBatchActions

components/email/email-viewer.tsx

@@ -2781,6 +2781,7 @@ export function EmailViewer({
             variant="default"
             size="sm"
             onClick={() => onEditDraft()}
+            data-testid="edit-draft"
             className="sm:flex sm:flex-row sm:h-8 sm:gap-1.5 sm:py-0"
             title={t('tooltips.edit_draft')}
           >

components/ui/context-menu.tsx

@@ -157,12 +157,15 @@ interface ContextMenuSubMenuProps {
   icon?: React.ComponentType<{ className?: string }>;
   label: string;
   children: React.ReactNode;
+  /** Stable hook for integration tests (not user-visible). */
+  testId?: string;
 }
 
 export function ContextMenuSubMenu({
   icon: Icon,
   label,
   children,
+  testId,
 }: ContextMenuSubMenuProps) {
   const [isOpen, setIsOpen] = useState(false);
   const [subMenuPos, setSubMenuPos] = useState<Position | null>(null);
@@ -236,6 +239,7 @@ export function ContextMenuSubMenu({
         role="menuitem"
         aria-haspopup="true"
         aria-expanded={isOpen}
+        data-testid={testId}
       >
         {Icon && <Icon className="w-4 h-4 flex-shrink-0" />}
         <span className="flex-1">{label}</span>