feat(ui): render the status chips and their split-flap labels from a store

ShellFeedback publishes the loading status and the road network chip, and
CctvControls the camera grid chip, to the gev-status store; the scene
chrome renders them. SplitFlapText plays the departure-board cascade that
splitFlap.js plans, writing only the label's one text node, and rests when
its owner is destroyed. setSplitFlapText and disposeSplitFlap are gone.

src/ui/stores/status.js

@@ -0,0 +1,44 @@
+import { defineStore } from 'pinia';
+import { markRaw, shallowRef } from 'vue';
+
+/**
+ * The scene's status chips as their views render them. ShellFeedback
+ * (src/ui/shellFeedback.js) publishes the top-center loading status and the
+ * road network chip, CctvControls the camera grid chip. Each label keeps its
+ * last text while hidden, so the next change flaps from what was shown.
+ */
+export const useStatusStore = defineStore('gev-status', () => {
+  /**
+   * `{hidden, state, label, detail, stopped}`; null until first published.
+   * `stopped` rests a label for good once its owner is destroyed.
+   */
+  const loading = shallowRef(null);
+  /** `{visible, label, immediate, progress, stopped}`, or null. */
+  const traffic = shallowRef(null);
+  /** `{visible, label, immediate, progress, stopped}`, or null. */
+  const cctv = shallowRef(null);
+
+  /** @param {?object} next A fresh presentation of the loading status. */
+  function publishLoading(next) {
+    loading.value = next && markRaw(next);
+  }
+
+  /** @param {?object} next A fresh presentation of the road network chip. */
+  function publishTraffic(next) {
+    traffic.value = next && markRaw(next);
+  }
+
+  /** @param {?object} next A fresh presentation of the camera grid chip. */
+  function publishCctv(next) {
+    cctv.value = next && markRaw(next);
+  }
+
+  return {
+    loading,
+    publishLoading,
+    traffic,
+    publishTraffic,
+    cctv,
+    publishCctv,
+  };
+});