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/src/model/id.ts

@@ -0,0 +1,13 @@
+/**
+ * Stable, collision-resistant identifier for blocks. Block ids survive
+ * split/merge/move and are how positions, selections, and the CRDT address a
+ * block — so they must be unique and never reused.
+ */
+export function createId(): string {
+  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function')
+    return crypto.randomUUID();
+
+  // Fallback for exotic runtimes without WebCrypto (Node >= 19 and all target
+  // browsers provide `crypto.randomUUID`, so this is effectively dead code).
+  return `b-${Math.random().toString(36).slice(2)}-${Date.now().toString(36)}`;
+}