Sort a notebook, import Markdown back, and stop the page shrinking in Draw

The paper measurably shrank on switching to Draw — 733px to 460px on the same
screen. The editor was a flex item at its default `flex: 0 1 auto`, so its width
was its widest row's: the toolbar. Swapping a dozen formatting buttons for six
drawing ones collapsed it. It now fills the pane, so the width is a property of
the window.

Each notebook remembers how its notes are ordered, on the server rather than per
device. The manual order has to survive being looked away from, so `reindex`
renumbers every note in the notebook rather than the filtered view, and dragging
is switched off while a search narrows the list. Reordering has its own route:
`PUT /notes/:id` would bump `updated_at` and snapshot a version, so a drag would
move a note to the top of "last changed" and spend a slot of its history.

Markdown and our own ZIP archives come back as notes, with their images
re-uploaded as attachments. A drawing returns as the PNG it was exported as —
vectors are not recoverable from pixels — and the import says so rather than
leaving it to be discovered. Writing the parser turned up a real bug in the
exporter: blocks were emitted with no blank line between them, so a list after a
list became one list and a quote after an item was read as part of it.

Creating or importing from "All Notes" now asks which notebook instead of
silently taking the first one. The web-link prompt is a real dialog: a bare
domain becomes https, javascript: is refused with a reason. The PDF viewer's
hide-drawing control is a labelled button rather than a filled-or-hollow dot,
and the export icon points down into a tray like every other download.

186 unit tests, 179 browser checks across eleven suites, including a new
`offline` suite that loads the app cold with the network off.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/hooks/useNoteData.ts

@@ -3,6 +3,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 import * as sync from "../syncEngine";
 import * as searchIndex from "../search";
 import { sameStrokeDoc } from "../features/drawing/strokes.js";
+import { reindex } from "../features/notes/noteSort";
 import type { Backlink, NoteContent, NoteMeta, Notebook, StrokeDoc, User } from "../types";
 
 /** How often the whole account is reconciled with the server. */
@@ -44,6 +45,8 @@ export interface NoteData {
   permanentDeleteNote: (id: string) => Promise<void>;
   emptyTrash: () => Promise<void>;
   moveNote: (id: string, folderId: string) => Promise<void>;
+  /** Drag-to-reorder within a notebook; only meaningful in manual sort. */
+  reorderNotes: (dragId: string, targetId: string) => void;
 
   createNotebook: (fields: { name: string; cover: number }) => Promise<Notebook>;
   updateNotebook: (id: string, updates: Partial<Notebook>) => Promise<void>;
@@ -261,6 +264,25 @@ export function useNoteData(user: User | null, activeNote: string | null): NoteD
     setNotes((p) => p.map((n) => (n.id === id ? { ...n, folderId } : n)));
   }, []);
 
+  /**
+   * Puts one note where another was, in the user's own order.
+   *
+   * The new positions are computed over *every* note in that notebook, taken
+   * from the store rather than from whatever the list is currently showing. A
+   * search or a filter must never be able to renumber the notes it is hiding.
+   */
+  const reorderNotes = useCallback((dragId: string, targetId: string) => {
+    const dragged = notesRef.current.find((n) => n.id === dragId);
+    if (!dragged) return;
+    const inNotebook = notesRef.current.filter((n) => !n.trashed && n.folderId === dragged.folderId);
+    const order = reindex(inNotebook, dragId, targetId);
+    if (!order) return;
+
+    const position = new Map(order.map((id, i) => [id, i]));
+    setNotes((p) => p.map((n) => (position.has(n.id) ? { ...n, sortOrder: position.get(n.id)! } : n)));
+    void sync.reorderNotes(order);
+  }, []);
+
   /* ── Notebooks ── */
 
   const createNotebook = useCallback(async (fields: { name: string; cover: number }) => {
@@ -311,6 +333,7 @@ export function useNoteData(user: User | null, activeNote: string | null): NoteD
     permanentDeleteNote,
     emptyTrash,
     moveNote,
+    reorderNotes,
     createNotebook,
     updateNotebook,
     deleteNotebook,