Arrange tool, and a hold that is easier to find

An Arrange tool marks the corners of every image, Hide and own text
rectangle in blue and moves or resizes them by a plain drag, a press
elsewhere doing nothing.  The hold that does the same with any tool is
shorter (450 ms), with more slack, and shows all four corners.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

client/index.html

@@ -45,7 +45,7 @@
       <button type="button" data-tool="pen" aria-pressed="true"
               data-help="Write on the page. Only your own writing can be erased.">Pen</button>
       <button type="button" data-tool="text" aria-pressed="false"
-              data-help="Type on the page. Tap where the text should begin, or drag open a rectangle: a red box, white inside, in which the text wraps and which grows downward as you type. Tap your own text to change it; rest the pen on it to move it, or near a corner of a box to resize it.">Text</button>
+              data-help="Type on the page. Tap where the text should begin, or drag open a rectangle: a red box, white inside, in which the text wraps and which grows downward as you type. Tap your own text to change it; rest the pen on it to move it, or near a corner of a box to resize it, or use Arrange.">Text</button>
     </div>
     <div id="settings" class="settings">
     <div class="group" id="colors" role="radiogroup" aria-label="Color">
@@ -64,9 +64,11 @@
              aria-label="Text size in points" data-help="Text size in points.">
     </div>
     </div>
-    <div class="group after_settings" role="radiogroup" aria-label="Hide and Eraser">
+    <div class="group after_settings" role="radiogroup" aria-label="Hide, Arrange and Eraser">
       <button type="button" data-tool="hide" aria-pressed="false" hidden
-              data-help="Hide part of the page for everyone: drag open a rectangle, and what lies under it is covered in white, marked by blue corners. Rest the pen on it to move it, or near a corner to resize it; a tap of the eraser removes it.">Hide</button>
+              data-help="Hide part of the page for everyone: drag open a rectangle, and what lies under it is covered in white, marked by blue corners. Rest the pen on it to move it, or near a corner to resize it, or use Arrange; a tap of the eraser removes it.">Hide</button>
+      <button type="button" data-tool="arrange" aria-pressed="false"
+              data-help="Move and resize: the corners of every image, Hide and text box of yours are marked in blue. Drag inside one to move it, drag a corner to resize it (an image keeps its shape). A press elsewhere does nothing. With any other tool, resting the pen on one of them for half a second does the same.">Arrange</button>
       <button type="button" data-tool="eraser" aria-pressed="false"
               data-help="Erase your own strokes and text by moving over them. A tap on an image, or on a Hide rectangle, removes it, if you are the host or a co-host (or added the image yourself). Two quick taps on empty paper, away from anything the eraser would remove, undo your latest mark; again, and the one before.">Eraser</button>
     </div>