feat(writekit): rename @robonen/editor to @robonen/writekit

Rename the rich-text editor package and all Editor* exports to Writekit*;
remove the old vue/editor tree.

vue/writekit/playground/src/demos/ReadOnlyDemo.vue

@@ -0,0 +1,18 @@
+<script setup lang="ts">
+import { WritekitRoot } from '@writekit';
+import { h, makeWritekit, p, t } from '../lib';
+
+const writekit = makeWritekit([
+  h(2, 'Read-only'),
+  p([t('You can '), t('select', 'bold'), t(' and copy this text, but typing and shortcuts do nothing.')]),
+  p('Mouse selection and arrow navigation still work across blocks.'),
+]);
+</script>
+
+<template>
+  <section>
+    <h2>Read-only</h2>
+    <p class="hint">editable=false — selection/navigation work; edits and shortcuts are blocked.</p>
+    <WritekitRoot :writekit="writekit" :editable="false" class="writekit" />
+  </section>
+</template>