feat(ui): render the Cockpit briefing card from a store

The Cockpit controller no longer writes the briefing card's pages, cycle
toggle, regional news and local conditions: it keeps them as plain state,
starting from cockpitBriefPages.js, and publishes a copy to a new
gev-cockpit store. A new CockpitBriefing component, lifted verbatim from
the Cockpit view, renders it. News rows are keyed by story, so a focused
link never turns into another story on refresh. The controls keep the
controller's listeners; the route card and the signal list keep their
owners' bindings for now. The boot-time kicker translation is gone, as
the card translates its own text.

src/ui/stores/cockpit.js

@@ -0,0 +1,19 @@
+import { defineStore } from 'pinia';
+import { markRaw, shallowRef } from 'vue';
+
+/**
+ * Cockpit content as its views render it. The Cockpit controller presents
+ * the briefing card's pages, cycle toggle, regional news and local
+ * conditions and publishes them here; it keeps the controls' listeners.
+ */
+export const useCockpitStore = defineStore('gev-cockpit', () => {
+  /** The presented briefing; null until the controller first presents it. */
+  const brief = shallowRef(null);
+
+  /** @param {?object} next A fresh presentation of the briefing card. */
+  function publishBrief(next) {
+    brief.value = next && markRaw(next);
+  }
+
+  return { brief, publishBrief };
+});