feat(frontend): assemble accessible application shell

frontend/src/components/StreamError.vue

@@ -0,0 +1,37 @@
+<script setup lang="ts">
+defineProps<{ code: string; message: string }>()
+defineEmits<{ retry: [] }>()
+</script>
+
+<template>
+  <div class="error" role="alert" :data-error-code="code">
+    <p>{{ message }}</p>
+    <button type="button" @click="$emit('retry')">Edit and retry</button>
+  </div>
+</template>
+
+<style scoped>
+.error {
+  padding-left: var(--s-5);
+  color: var(--c-error);
+  border-left: 2px solid var(--c-error);
+}
+
+.error p {
+  margin: 0;
+  text-wrap: pretty;
+}
+
+.error button {
+  min-height: var(--tap-min);
+  margin-top: var(--s-3);
+  padding: 8px var(--s-4);
+  color: var(--c-error);
+  font-family: var(--f-mono);
+  font-size: var(--t-micro);
+  background: transparent;
+  border: 1px solid currentcolor;
+  border-radius: var(--r-md);
+  cursor: pointer;
+}
+</style>