docs: the readouts strip follows the collapsed state

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

docs/claude/invariants-readouts-and-cursors.md

@@ -58,7 +58,7 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   compares `gtk_label_get_text()` (the untruncated text) of every dock label with the page's, and
   `fits=1` that the Readouts box is no wider than the dock.
 - **The readouts strip is a third reader of the same string, never a second formatter.** When the dock is
-  not on screen the readouts are shown in the strip under the plot (`readouts_strip`, `src/ui_dock.cpp`): the
+  not beside the plot (hidden, or the window collapsed so the dock is an overlay) the readouts are shown in the strip under the plot (`readouts_strip`, `src/ui_dock.cpp`): the
   cursor chips' `who` and *delta* labels and the measurement chips' value labels. They are written **in the
   same call** as the dock's -- `dock_cursor_cell()` and `dock_measure_value()` set the strip's label from the
   argument they were handed, and `dock_rebuild_cursors()` / `dock_rebuild_measures()` rebuild its chips