docs: events in the dock and on its page

The dock's Events block, the events slide-over page, the availability-rule deviation, the probe lines and the removal of the left pane are described; the false remembered-width claim is gone.

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

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

@@ -210,9 +210,10 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   entry points in `source_dialog.cpp` (`chooser_tour_begin`, `chooser_tour_autostart`), and *that* walk
   is what a first run meets first -- see the tour bullets in the help-affordance section below.
 - **A `GtkPaned` hands its start child at least its minimum unless the position says otherwise.**
-  Putting the events pane in a paned is what makes its width the user's to drag -- but with the
-  position left alone, `shrink-start-child` or not, the pane's minimum is reserved as an empty column
-  while it is *closed*, and the plot pays for a pane nobody opened. The position is the only knob that
+  (The events pane that taught this is gone -- its list is a slide-over page now, with no divider -- but
+  the rule holds for any paned.) With the
+  position left alone, `shrink-start-child` or not, a closed side child's minimum is reserved as an empty
+  column, and the plot pays for a pane nobody opened. The position is the only knob that
   says "no room": store the width when it is closed (reading `gtk_paned_get_position()` *before*
   zeroing it) and set 0, restoring it when the pane opens. `gtk_paned_set_shrink_start_child(TRUE)` is
   still needed, or the minimum would clamp even a zero position.
@@ -220,7 +221,8 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   = FALSE` makes both the revealer's minimum and its natural size zero -- and its box then hands it
   everything the expanding sibling beside it did not claim, so a *collapsed* pane reserved a
   310-pixel empty column between the window edge and a plot drawn 630 pixels wide in a 1270-pixel
-  window. Every vertical revealer in the side panel hides this, because there the leftover goes down
+  window. (That pane was a revealer beside the plot; it is a slide-over page now, so no revealer sits in
+  a horizontal box any more.) Every vertical revealer in the side panel hid this, because there the leftover goes down
   instead of across. `gtk_widget_set_visible()` is what a layout honours, so anything that must not
   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.
@@ -278,8 +280,9 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   clicked — a switch that greyed out with its own pane could never turn it back on. That is why the
   sensitive target is the pane's **body** (`trigger_body`, `cursors_body`) and not the pane.
 - **A list box outlives the children of the pane it sits in, and the teardown order is not yours to
-  choose.** Tearing the window down finalizes the events pane's buttons, then the list box, and the
-  list's own `selected-rows-changed` then reaches a handler holding the freed pointers: four
+  choose.** Tearing the window down finalizes the events page's buttons, then its list box, and the
+  list's own `selected-rows-changed` then reaches a handler holding the freed pointers (`update_group_buttons()`
+  therefore keeps its `app.window == nullptr` guard): four
   `Gtk-CRITICAL`s from `gtk_widget_set_sensitive` and a read of memory nobody owns. `close-request` is
   *not* the hook -- `UDPSCOPE_EXIT_AFTER_MS` ends the self-check with `gtk_window_destroy()`, which does
   not emit it. The hook that does work is `App::window`: every teardown path clears it *before* the
@@ -296,22 +299,26 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
 - **A pointer to a widget inside a list survives the list being rebuilt.** `events_thumb` named a row's
   picture across `refresh_events_pane()`, which removes every row first: the next reader of that
   pointer got a `Gtk-CRITICAL` from `gtk_picture_get_paintable` on freed memory (the four criticals
-  read as "the pane is empty"). A rebuild has to null what it is about to destroy, not only rebuild it.
+  read as "the page is empty"). A rebuild has to null what it is about to destroy, not only rebuild it
+  (`rebuild_events_pane_list()`, the page half of `refresh_events_pane()`, nulls `events_thumb` before it removes the page list's children). A handler on a
+  row that rebuilds the list destroys the widget it was emitted from: `outlive_the_rebuild(widget)`. The dock's
+  rows are a second list built from the same records; the dock row's click handler is safe only because
+  `replay_event()` never rebuilds the dock list.
 - **`gtk_picture_set_filename()` can render nothing, silently.** It hands the file to the image
   loader's sandboxed, asynchronous decoder, which on this machine fails without a message: the
   picture keeps a *paint-able* and takes an allocation, so a probe that checks
-  `gtk_picture_get_paintable()` reads success while the pane shows an empty rectangle (the event
-  pane's preview did exactly that). `gdk_texture_new_from_filename()` decodes the same file on this
+  `gtk_picture_get_paintable()` reads success while the page shows an empty rectangle (the event
+  page's preview did exactly that). `gdk_texture_new_from_filename()` decodes the same file on this
   thread and `gtk_picture_set_paintable()` hands over the result -- and a NULL texture at least says
   so. A picture that must be on screen is also a picture with a **height request**: `can_shrink`
   alone asks for no height at all in a box.
 - **A cache that is the *only* source of a widget's content must be created by the thing that reads
-  it.** The event pane's thumbnails come from an `EventThumbCache` hung off the list box with
+  it.** The events page's thumbnails (the dock's rows have none) come from an `EventThumbCache` hung off the page's list box with
   `g_object_set_data_full`, and `event_preview_texture()` answers out of that cache or not at all.
-  Nothing ever created it — so for as long as the pane existed, **every** row came up without a
+  Nothing ever created it — so for as long as the list existed, **every** row came up without a
   picture, which is what "event screenshot are unusable and sometime missing" was. A missing cache
   there is not a slow path, it is a blank one; `event_thumb_cache()` therefore creates one on first
-  use. Owned by the **list**, because nothing else has the pane's lifetime: textures of a list that
+  use. Owned by the **list**, because nothing else has the page's lifetime: textures of a list that
   no longer exists are so much held memory, and the destroy notify is where they are unref'd.
 - **Hover magnification is a tooltip, not a popover of ours.** A row's thumbnail is 138 px wide and
   the stored preview is 480: the small one says *which* event this is, and the zoom says what is in