docs: the readouts dock, the cursors and measurement pages

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

docs/claude/architecture.md

@@ -101,8 +101,11 @@ touching the data path.
   a `slideover_add_page(app, id, title, widget)`: the widget is wrapped in a `GtkScrolledWindow` of its
   own and registered under its id (`trigger`, `source-<id>`, `signals` (the signal list) and
   `signal:<name>` (one signal's page, `src/ui_signal_page.cpp`, created on demand by `signal_page_ensure()`
-  and pruned by `signal_pages_sync()`, which `rebuild_signal_panels()` ends with); `measure`, `cursors`
-  and `events` are reserved for later steps). One page is open at a time and `App::slideover.page`
+  and pruned by `signal_pages_sync()`, which `rebuild_signal_panels()` ends with), `cursors` (the cursors
+  panel, unchanged) and `measure` (the measurements panel, unchanged; `m` toggles it); `events` is reserved
+  for a later step). Both of those are registered whether or not they are open (a closed page's widgets
+  exist, unmapped), and both are insensitive until the stream has signals, by the same
+  `update_signal_availability()` call that sets the dock's sensitivity. One page is open at a time and `App::slideover.page`
   is its id, empty when closed. The open page is **not** a session value. Esc, *Close*, a second click on the
   badge and a click on the plot close it; the click-away is a capture-phase observer (see
   [invariants-gtk-and-chrome.md](invariants-gtk-and-chrome.md)). With two or more `source-*` pages, an
@@ -116,9 +119,18 @@ touching the data path.
   file) leaves it **hidden** (the user asked for hide here, not the usual disable): `sync_badge_bar()` sets its visibility,
   pick and focus from `slideover.source_pages` being non-empty every tick, so anything that indexes the badge
   (the tour's `badges` step targets the whole bar, `[badges]`) must tolerate it being absent.
-- **The dock** is the `AdwOverlaySplitView` sidebar (`side_box` > `dock_scroller` > `dock_page`): the
-  cursors and the measurements only, in one scroller (the signal list is the `signals` page). It holds no tab switcher and no
-  revealer, and it does not hold a source kind's panels (those are slide-over pages).
+- **The dock** is the `AdwOverlaySplitView` sidebar (`side_box` > `dock_scroller` > `dock_page`), **280 px**
+  and fixed. It holds one thing, the **Readouts** box (`src/ui_dock.cpp`, `build_readouts_dock()`): a
+  **Cursors** block (heading, an **Edit** button that opens the `cursors` page, a `GtkGrid` of a header row
+  `A B delta` and one line per page line) and a **Measurements** block (heading, **Edit** opening the
+  `measure` page, one line per measurement: chip, type, value; a click on a line opens that measurement's
+  dialog; no measurements shows one dim "no measurements" line). It is read-only and **owns no formatting**:
+  `update_cursors_pane()` and `update_measures()` hand the string they wrote to the page's label to
+  `dock_cursor_cell()` / `dock_measure_value()` as well, and `rebuild_cursors_pane()` /
+  `rebuild_measures_pane()` end by rebuilding the dock's lines to match (`dock_rebuild_cursors()`,
+  `dock_rebuild_measures()`). It holds no tab switcher, no revealer and none of the full panels, nor a source
+  kind's panels (those are slide-over pages). The window's measurement editor is a dialog
+  (`open_measure_dialog()`), not part of the `measure` page.
 
 **When each is built and when it is read.** `build_slideover()` runs in `on_activate` right after the tour
 overlay is built (the tour's overlay wraps the whole window, so its dim rectangles cover the slide-over