feat(panels): render each panel's state classes from the store

A panel's collapsed, dock-pinned, dock-pinned-top, layout-auto-collapsed
and accordion-collapsed classes are drawn by its root's v-panel-state from
the gev-panel-chrome store. PanelChrome, its restore, the layout
controller, both rails and the side accordion present each panel's state
there instead of writing its classes; the rails call onCollapse(panel,
{collapsed, auto}). The directive applies a change in a synchronous
watcher, since the rails measure a panel in the task that opens or closes
it.

Destroying the chrome inside Cockpit now puts back the panels Cockpit's
entry closed while it can still present them. Without a shell, the voice
tools' set_panel_open reports that there is no panel to open. QA scripts
present the states they set instead of writing the classes.

scripts/qa-visual-input.mjs

@@ -57,7 +57,7 @@ try {
       persist: false,
       syncShare: false,
     });
-    manager._sliderPanel.classList.remove('collapsed');
+    manager._presentPanel(manager._sliderPanel, { collapsed: false });
     const slider = manager._sliderContainer.querySelector('input');
     window.__qaOldSlider = slider;
     const name = 'pixelation';