ui: a signal's page shows gain and offset as aligned rows with a pencil each, replacing Calibrate

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

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

@@ -30,8 +30,9 @@
       </item>
       <item>
         <p>Once a signal is acquired its badge appears. Click it to open that signal's page: its
-        colour, <gui>Plot on</gui> buttons for the rows, and <gui>Information</gui> and
-        <gui>Calibrate</gui>, where the signal's details and its calibration live.</p>
+        colour, <gui>Plot on</gui> buttons for the rows, <gui>Information</gui> for the signal's
+        details, and its <gui>Gain</gui> and <gui>Offset</gui>, each with a pencil button that
+        edits that one number.</p>
       </item>
     </steps>
   </section>
@@ -42,8 +43,9 @@
       <item><p>Signals start disabled, and enabling one is what starts acquiring it. A trigger
       on a signal nobody acquires can never fire, so arming a trigger enables its signal for
       you.</p></item>
-      <item><p><gui>Calibrate</gui> on a signal's page opens the gain and offset it is
-      <em>currently</em> drawn through, so a trace already scaled by a gain of 2 shows 2 —
+      <item><p>A signal's page shows the gain and offset it is <em>currently</em> drawn
+      through, so a trace already scaled by a gain of 2 reads 2. The pencil beside a number opens
+      an editor for that number only, at its current value —
       pressing <gui>Apply</gui> confirms it rather than resetting it. A signal nobody
       calibrated shows the identity, 1 and 0.</p></item>
       <item><p>Calibration is applied <em>at ingest</em>, so changing it re-plans the buffer