docs: the readouts strip

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

README.md

@@ -159,7 +159,19 @@ cells are a fixed number of characters wide and ellipsized, so the dock's width
 depend on what a value reads: the **who** cell of a cursor line is 5 characters (the full text is its
 tooltip), a value cell 9 (its tooltip is the full text). The dock and the pages show **one string**:
 `update_cursors_pane()` and `update_measures()` format each value once and hand that variable to the
-page's label and to the dock's, so the two cannot disagree. The **Events** block is a heading with a
+page's label and to the dock's, so the two cannot disagree. **When the dock is not on screen** -- hidden
+with the dock button, or the window narrow enough (< 900 px) for the dock to be a collapsed overlay that is
+not currently open -- 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).
+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
+same strings** (the setters that write the dock's labels write the strip's), and it is hidden whenever the
+dock is shown, so the plot never loses its 26 px to both. **Known limit:** a *collapsed* window whose dock
+button is still on has the dock overlaid over the plot (the app re-asserts the button's wish every frame, so
+the overlay cannot be swiped away), and then the strip is hidden; it shows once the dock button is off. 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
 picture -- and one click on a row replays that event (see "Captured events"). The full list, with the
 pictures and the comparison actions, is the `events` slide-over page that **Manage** opens. There is no