docs: the readouts dock, the cursors and measurement pages

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

docs/claude/invariants-gtk-and-chrome.md

@@ -50,7 +50,7 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   runs after the window is destroyed and asking GTK about a widget then is four criticals, which is
   how the first version of that line earned them. What stays in the menu is what acts on the *data*
   (Fit, Export, Configurations) and the one editor that is not a pane (the layout editor): the signal list
-  is a section of the sidebar's dock, so there is nothing left to reveal or hide about it. The Arm/Disarm button in the trigger panel still has text.
+  is the `signals` slide-over page, so there is nothing left to reveal or hide about it. The Arm/Disarm button in the trigger panel still has text.
 - **Five of this app's icons are its own, and they are a `GResource` compiled into the
   binary.** No icon theme has a glyph for an oscilloscope trigger, a pair of cursors or a
   measurement ruler, and the stock names those buttons used to carry said something else
@@ -225,13 +225,15 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   take room has to be hidden and not merely unrevealed; the revealer keeps the slide while the pane
   *is* open. The allocated width is how this was found -- the revealer's own measure said 0.
   **The sidebar is one dock now, and has no `GtkRevealer` left in it**: a single `GtkScrolledWindow`
-  (`dock_scroller`) holding the cursors and the measurements one under another. It
+  (`dock_scroller`) holding only the compact **readouts** (`src/ui_dock.cpp`). It
   replaced an `AdwViewSwitcher` over an `AdwViewStack`, whose four text tabs did not fit 320 px (and a source
   can add more); a source kind's own panels are slide-over pages, not dock sections. The reason is the one
-  this trap teaches: sections competing for one 320 px column each left every one of them short of room, and
-  a scroller gives each its natural height. `m` scrolls the dock to the cursors (`dock_show_section()`); the signal list is
-  not a dock section but the `signals` slide-over page, which `g` and the `+` badge open. A *feature's* on/off is no longer a visibility at all -- the
-  **cursors'** toggle sets its pane's **body** insensitive -- the readout has nothing to show with the
+  this trap teaches: full panels competing for one narrow column each left every one of them short of room.
+  The full cursors and measurements panels are now the `cursors` and `measure` **slide-over pages**, reached
+  by the readouts' **Edit** buttons, and `m` toggles `measure` (it no longer scrolls the dock;
+  `dock_show_section()` is gone); the signal list is the `signals` slide-over page, which `g` and the `+` badge
+  open. The header's Cursors toggle no longer opens anything: it only enables the cursors. A *feature's* on/off is no longer a visibility at all -- the
+  **cursors'** toggle sets its pane's **body** insensitive (and the dock's cursor grid beside it) -- the readout has nothing to show with the
   instruments off -- and the *body* and not the pane, because the pane's heading carries its own switch
   (see the next bullet). The **trigger's body is deliberately never disabled**: a trigger is configured
   *before* it is switched on, so switching it off to change it, or to read what it is set to, is the
@@ -243,7 +245,10 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
 - **The dock is shown but insensitive until the stream has signals ("disable, do not hide").**
   `update_side_visibility()` and the tick's per-frame block set the column's visibility from the user's wish
   alone (`sidebar_wanted`) and the dock's *sensitivity* from `have_signals`; the toolbar's Dock button stays
-  sensitive throughout. The wish is persisted (`dock = true|false` in the session file) and a change of it
+  sensitive throughout. The `cursors` and `measure` **pages follow the same condition** through
+  `update_signal_availability()` (called from `update_side_visibility()` and the per-frame block), so a
+  page opened by `m` before the stream has signals is insensitive, not refused. `[readouts] ... pages_sensitive=`
+  reads it. The wish is persisted (`dock = true|false` in the session file) and a change of it
   schedules a save. `dock:` in the dump reads the result.
 - **The signal badge is the drag handle, and a drop handler only moves widgets.** Dragging a signal onto a plot
   starts on its badge in the badge bar (a `GtkDragSource` on the badge's button, payload the signal index as a
@@ -584,6 +589,18 @@ The `Help` submenu, the contextual help's "?" and the guided tour, and the traps
   `ui_impl::hint_button()` reached either by the table's `context_help_sync()` or by
   `context_help_button()` for a window with no `App` (the source chooser) -- one button, two callers,
   so the two windows cannot drift into two affordances.
+- **A hint on a slide-over page's heading is attached all the time and drawn only while the page is open.**
+  The trigger's, signals', cursors' and measurements' headings (`trigger_head`, `signals_head`,
+  `cursors_head`, `measures_head`) live on pages that exist, unmapped, whether or not they are open, so
+  `context_help_sync()` attaches their "(i)" like any other and the count (`hints=12`) does not depend on
+  which page is up. There is **no second code path** and the dock's readouts carry no hint of their own: the
+  pages' hints say what the dock shows too (the cursors' and measurements' bodies mention the read-only copy
+  and the Edit button). A probe that must *see* one drawn needs its page open, like every other reading off a page.
+- **The tour has one stop for the readouts and none for the pages behind them.** The dock's stop
+  (`side`, target `side_box`, no `page`, so it closes the panel) describes the readouts, the **Edit**
+  buttons and the click on a measurement; the `cursors` and `measure` pages are reached from there rather than
+  walked. A stop for either would be one more `TourStop::page` (see the next bullet), and the plan's
+  length is asserted (`steps=6`, `steps=5` with the dock put away) -- a new stop changes both.
 - **The guided tour takes no grab, and that is the whole reason it is an overlay.** Four dim
   rectangles around the hole are ordinary widgets that swallow the clicks that land on them and
   nothing else; `Skip`, `Finish` and `Escape` hide them, and there is no popover, no gesture and no