docs: the readouts strip hides when empty

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

README.md

@@ -164,12 +164,17 @@ with the dock button, or the window narrow enough (< 900 px, "compact mode") for
 overlay on the plot, open or not -- the same readouts appear on **one line under the plot**, above the badge bar (the
 *readouts strip*): a **Cursors** button (opens the `cursors` page) and one chip per cursor line (its name and
 its *delta* value), then a **Measures** button (opens the `measure` page) and one chip per measurement (the
-signal's colour chip, the type, the value; a click opens its dialog; "no measurements" when there are none).
+signal's colour chip, the type, the value; a click opens its dialog). Each of the two groups is there only
+with something to read -- the Cursors group with the cursors switched on, the Measures group with at least one
+measurement, the separator with both -- and **with neither, the strip is not shown at all**.
 It is a **fixed 26 px** high and its chips are as wide as the dock's cells (name 6 characters, type 10, value
 9, the full text in the tooltip); what does not fit scrolls sideways with no bar taking height. With the
-cursors off the chips are insensitive and read `--`, as the dock's cells do. It is the **third reader of the
+cursors off their chips are insensitive and read `--`, as the dock's cells do (the group is hidden then, so this is
+not seen). It is the **third reader of the
 same strings** (the setters that write the dock's labels write the strip's), and it is shown exactly when
-`!show-sidebar || collapsed`: in a wide window it is hidden while the dock is shown beside the plot (so the
+`(!show-sidebar || collapsed)` **and** (the cursors are on **or** there is a measurement) -- a deliberate
+exception to "disable, do not hide": an empty line under the plot is 26 px of nothing, and the dock, which keeps
+both blocks on screen, is where the empty state is shown. In a wide window it is hidden while the dock is shown beside the plot (so the
 plot never loses its 26 px to both), and in a collapsed window it stays on screen even with the dock overlaid,
 so the measurements and cursors remain visible in compact mode. The **Events** block is a heading with a
 **Manage** button over a short list of the cached events, newest first -- one compact row each, never a