docs: the readouts strip hides when empty

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

docs/claude/architecture.md

@@ -137,9 +137,13 @@ touching the data path.
   **The readouts strip** (`readouts_strip` in `main-window.ui`, between `plot_overlay` and `badge_bar` in
   `left_column`; filled by `ui_dock.cpp`) carries the same readouts when the dock is not beside the plot: a flat
   **Cursors** button and one chip (`who` + delta) per cursor line, then a **Measures** button and one chip per
-  measurement. `sync_readouts_strip()` shows it exactly when `!adw_overlay_split_view_get_show_sidebar() ||
-  adw_overlay_split_view_get_collapsed()` -- the Dock button put the dock away, or the window is collapsed and
-  the dock is an overlay on the plot (the strip stays on screen even while that overlay is open). The tick
+  measurement. `sync_readouts_strip()` shows it exactly when `(!adw_overlay_split_view_get_show_sidebar() ||
+  adw_overlay_split_view_get_collapsed())` **and** (the cursors toggle is active **or** `app.measures` is
+  non-empty) -- the Dock button put the dock away, or the window is collapsed and the dock is an overlay on the
+  plot (the strip stays on screen even while that overlay is open), and there is something to read. Inside, the
+  Cursors group (`strip_cursor_group`) is shown with the cursors on, the Measures group (`strip_measure_group`)
+  with measurements, the separator (`strip_sep`) with both; with neither the strip is hidden. Besides the tick,
+  the cursors toggle handler and `rebuild_measures_pane()` call it, so a toggle or an add/delete shows at once. The tick
   calls it right after re-asserting `sidebar_wanted` and *before* `set_collapsed()` (so the split view's own
   collapse-time `show-sidebar` write is never read); that means the `collapsed` it reads is the previous
   frame's, and the strip follows a collapse or a widening one tick late, never through a wrong state. Its labels (`strip_cursor_who`, `strip_cursor_deltas`, `strip_measure_labels`) are rebuilt by