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.

src/ui/rightPanelRail.js

@@ -41,7 +41,8 @@ function settledLeftRailTop(leftStack, viewportHeight, getComputedStyle) {
  * @param {Window} options.windowRef Viewport and style reader.
  * @param {{visible: boolean, variant: string}} options.hud Current HUD presentation.
  * @param {string} options.preferredPanelId Most recently opened panel.
- * @param {Function} options.onCollapse Update a panel's disclosure chrome.
+ * @param {Function} options.onCollapse Present a panel's collapse:
+ *   `(panel, {collapsed, auto})`.
  * @param {Function} options.onRetry Request another pass after automatic collapse.
  * @param {Function} [options.getComputedStyle] Optional DOM style reader override.
  * @param {HTMLElement} options.leftStack Rail supplying the shared top baseline.
@@ -83,8 +84,7 @@ export function layoutRightPanelRail({
     for (const panel of panels.filter((item) =>
       item.classList.contains('layout-auto-collapsed'),
     )) {
-      panel.classList.remove('collapsed', 'layout-auto-collapsed');
-      onCollapse(panel);
+      onCollapse(panel, { collapsed: false, auto: null });
     }
   }
   // One panel is open per desktop side; this marker is distinct from
@@ -275,8 +275,7 @@ export function layoutRightPanelRail({
   if (!isCollapseRetry && autoCollapseIndices.length) {
     for (const index of autoCollapseIndices) {
       const panel = expandedPanels[index];
-      panel.classList.add('collapsed', 'layout-auto-collapsed');
-      onCollapse(panel);
+      onCollapse(panel, { collapsed: true, auto: 'layout' });
     }
     pendingCollapseRetries.add(stack);
     onRetry();