Load the composer, previews, dialogs and other sidebars on demand

The main chunk carried everything the mail view might open: the file
preview and its Markdown renderer, the composer and its editor, the contact
editor, the filter and share dialogs, and the calendar, contacts and files
sidebars. Each is now loaded when first shown. The composer is also
fetched when the browser is idle after startup, so the first Compose does
not wait on the network.

Import the notification helpers statically where they already were: the
dynamic imports beside those static ones split nothing.

web/src/views/mail/MessageList.tsx

@@ -1,4 +1,4 @@
-import { Fragment, memo, useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState, type DragEvent, type MouseEvent, type ReactNode } from "react";
+import { Fragment, lazy, memo, Suspense, useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState, type DragEvent, type MouseEvent, type ReactNode } from "react";
 import { useVirtualizer } from "@tanstack/react-virtual";
 import { useShallow } from "zustand/react/shallow";
 import { Archive, ArrowLeft, CalendarDays, CalendarRange, CalendarPlus, CheckSquare, FolderInput, PanelRight, PanelBottom, PanelTop, Filter, Inbox, Mail, MailOpen, MailPlus, MoreVertical, Paperclip, RefreshCw, Reply, Search, Star, Tag, Trash2, AlertOctagon, Forward, Eraser, ShieldCheck, X } from "lucide-react";
@@ -21,9 +21,11 @@ import { startAppointment } from "@/lib/calendar/appointment";
 import { toast } from "@/ui/toast";
 import { haptic, usePullToRefresh, useTouchRow, PULL_TRIGGER } from "@/lib/input/touch";
 import { describeSwipe, type SwipeAction, type SwipeDescriptor, type SwipeIcon } from "@/lib/input/swipe";
-import { FilterFromMessageDialog } from "./FilterFromMessage";
 import { plural, t } from "@/lib/i18n";
 
+// Loaded when first opened: it is not needed to show mail, and it is not small.
+const FilterFromMessageDialog = lazy(() => import("./FilterFromMessage").then((m) => ({ default: m.FilterFromMessageDialog })));
+
 /**
  * The glyph on the strip a swipe reveals. Sized larger than the toolbar's
  * icons: it is read at arm's length, in motion, out of the corner of an eye.
@@ -560,7 +562,7 @@ export function MessageList({ title, list, openThreadId, openMessageId, focusId,
         <MenuItem icon={<Filter size={16} />} label={t("Filter messages like this…")} onClick={() => { const e = ctxRow ? emails[ctxRow] : undefined; if (e) setFilterFrom(e); }} />
         {hasCalendar && <MenuItem icon={<CalendarPlus size={16} />} label={t("Create event…")} onClick={() => { const e = ctxRow ? emails[ctxRow] : undefined; if (e) void startAppointment(e, navigate).catch((err: unknown) => toast.error((err as Error).message)); }} />}
       </Popover>
-      {filterFrom && <FilterFromMessageDialog email={filterFrom} mailboxId={mailboxId} onClose={() => setFilterFrom(null)} />}
+      {filterFrom && <Suspense fallback={null}><FilterFromMessageDialog email={filterFrom} mailboxId={mailboxId} onClose={() => setFilterFrom(null)} /></Suspense>}
     </div>
   );
 }