docs: the sample budget in samples per signal, the memory limit and the planner probe lines

Converts every --buffer-mb / buffer_mb mention to --buffer-samples / buffer_samples,
records the unit change as a deviation (README, SPECS, CLAUDE.md), documents the
buffer: and planner: dump lines and the new Preferences row, and updates the help
pages and the help-shot script.

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

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

@@ -18,7 +18,7 @@
     <p>udpscope plots a live UDPStreamer source. One window holds up to eight rows of plots,
     each with up to four traces, and every row shares one time axis, so the whole figure
     scrolls together. Acquisition runs on its own thread and writes a ring buffer sized from
-    <cmd>--buffer-mb</cmd>; the drawing thread reads whatever that ring holds when a frame
+    <cmd>--buffer-samples</cmd>; the drawing thread reads whatever that ring holds when a frame
     starts, which is why a trace never makes the window stutter.</p>
 
     <p>The stream is the clock. Every interval you read on screen is measured between

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

@@ -41,7 +41,7 @@
     they open.</p>
 
     <p>A configuration also carries the settings that can only be decided when the buffers are
-    allocated: the <gui>buffer size</gui> (<cmd>--buffer-mb</cmd>), relative time, and the
+    allocated: the <gui>samples per signal</gui> (<cmd>--buffer-samples</cmd>), relative time, and the
     packet capture's ring size. Opening a configuration from the chooser applies all three;
     switching inside a running app applies the rest and says in the status line that these take
     effect on the next start.</p>
@@ -57,8 +57,8 @@
     <list>
       <item><p>What a configuration persists: the time window, the rows and each row's slot
       signals, the calibration, the trace colours, which signals were enabled, the math
-      channels with their graphs, the measurements pane — and the startup settings: buffer
-      size, relative time and the packet capture's ring size.</p></item>
+      channels with their graphs, the measurements pane — and the startup settings: samples
+      per signal, relative time and the packet capture's ring size.</p></item>
       <item><p>Signal identity is the <em>name</em> throughout, because a new CONFIG renumbers
       the channels.</p></item>
       <item><p>A file written by a run against a source whose streamer was down would name no

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

@@ -28,7 +28,7 @@
         stored <em>configuration</em> (<code>host:port · name</code>, its note, and the
         settings it carries), newest first, plus a <gui>New host…</gui> form that takes the
         address <em>and</em> the configuration it belongs to — its name and note, the
-        <gui>buffer size</gui>, and whether time is relative or absolute. A row's pencil
+        <gui>samples per signal</gui>, and whether time is relative or absolute. A row's pencil
         button opens the same form on that configuration, pre-filled, and changes to its name
         or address move it (the old file is deleted).</p>
       </item>

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

@@ -117,7 +117,7 @@
       layout the app starts with — has room for one older acquisition of each of them; a row per
       signal has room for all seven.</p></item>
       <item><p><em>Memory.</em> A retained acquisition is a whole window copied out of the ring,
-      so persistence may hold at most as much again as the buffer (<gui>--buffer-mb</gui>) does.
+      so persistence may hold at most as much again as the buffer takes (see <cmd>--buffer-samples</cmd> and <cmd>--memory-limit-mb</cmd>).
       On a long window at a high sample rate that bound is reached before the eighth layer.</p></item>
     </list>
   <section id="persistence">

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

@@ -56,11 +56,10 @@
 
   <section id="example">
     <title>Example</title>
-    <p>1 MS/s with 200 MB of buffer. A 2 s window stores every sample
-    (<code>time x1</code>). Widen it to 600 s and the stride becomes <code>x16</code>: 625 S/s
-    stored, anti-aliased at 312.5 Hz. A 2 kHz sine seen through that window reads
-    <code>y=[-0.059, 0.079]</code> — attenuated to about 6%, not folded down to a
-    full-amplitude 125 Hz one.</p>
+    <p>1 MS/s with the default buffer of 8 388 608 samples per signal (8.39 s). A 2 s window
+    stores every sample (<code>time x1</code>). Widen it to 600 s and the stride becomes
+    <code>x128</code>: 7.8 kS/s stored, anti-aliased at 3.9 kHz. A 5 kHz sine seen through that
+    window is attenuated by the filter, not folded down to a full-amplitude low-frequency one.</p>
   </section>
 
 </page>