docs: the readouts dock, the cursors and measurement pages

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

help/C/org.udpscope.app/measurements.page

@@ -28,10 +28,10 @@
     <title>How to reach it</title>
     <steps>
       <item>
-        <p>Press the measurements button in the toolbar, or <key>m</key>.</p>
+        <p>Press <key>m</key>, or <gui>Edit</gui> beside <gui>Measurements</gui> in the side panel.</p>
       </item>
       <item>
-        <p>The pane's <gui>+</gui> adds one; clicking a row opens the dialog where the signal,
+        <p>The panel's <gui>+</gui> adds one; clicking a row opens the dialog where the signal,
         the type, the threshold share or shares and the on-plot marks are set, with
         <gui>Save</gui> and <gui>Delete</gui>.</p>
       </item>