feat(panels): render collapse, dock and pin buttons from the store

PanelChrome no longer writes the panels' collapse buttons, the command
dock tray toggles' names or the dock pins' pressed state. It presents each
panel's open and pinned state to the new gev-panel-chrome store, and the
buttons, now views, call it there: PanelCollapseButton for the panel
headers, bound toggles and pins in the command dock. Clicks take effect
once the chrome is initialized; a new owner starts from its own states.

bindPanelDisclosure binds only a panel's Escape and refuses the retired
buttons and onChange arguments. UiButton joins the component kit.

src/streetLevelMarkup.test.mjs

@@ -22,7 +22,7 @@ test('Street Level is a collapsible right-rail panel that starts collapsed', ()
   );
   assert.match(
     html,
-    /<button class="panel-collapse-btn" data-collapse-target="street-level-panel"/,
+    /<button type="button" class="[^"]*\bpanel-collapse-btn\b[^"]*"[^>]*data-collapse-target="street-level-panel"/,
   );
   assert.match(
     html,
@@ -46,9 +46,10 @@ test('the panel is registered with panel chrome, cockpit entry and the right rai
     panelChrome,
     /COCKPIT_ENTRY_COLLAPSE_PANEL_IDS = Object\.freeze\(\[[\s\S]*'street-level-panel'/,
   );
+  // A right-rail panel's collapse button opens sideways (◀ / ▶).
   assert.match(
-    panelChrome,
-    /const isRightRail = \[[\s\S]*'street-level-panel'/,
+    read('src/ui/views/panels/StreetLevelPanel.vue'),
+    /<PanelCollapseButton[^>]*target="street-level-panel"[^>]*\bsideways\b/,
   );
   assert.match(
     layoutController,