Expose reusable builder kit surfaces and email preset pack

packages/block-editor/README.md

@@ -1,4 +1,42 @@
 # @wrnexus/block-editor
 
-Hydrated editor state and DOM runtime for portable block documents. All changes
-flow through validated `@wrnexus/blocks` commands; DnD produces move intents.
+Reusable editor state, DOM surfaces, inspector drafts, clipboard-download UI,
+selection actions, and explicit block/preset composition.
+
+## Configure a builder
+
+```ts
+import { createBuilderKit, createBlockEditorState, mountBlockCanvas } from "@wrnexus/block-editor";
+import { emailEditorBlocks } from "@wrnexus/email-renderer/create";
+import { emailPresets } from "@wrnexus/email-renderer/presets";
+
+const builder = createBuilderKit({
+  blocks: [...emailEditorBlocks, myTrustedBlockDefinition],
+  presets: [...emailPresets, myTrustedSectionPreset],
+});
+
+const palette = builder.blocks(); // manifests: name, icon, category, schemas
+const presets = builder.presets();
+const node = builder.createBlock("custom.my-block", { id: () => crypto.randomUUID() });
+```
+
+Definitions use `defineBlock` from `@wrnexus/blocks`: manifest, create,
+renderers, textRenderer, inspector controls, and migrations. Presets have
+`id`, localized `name`, `icon`, and `create({ id })`. Registration is
+explicit and frozen; duplicates and invalid created trees throw before insertion.
+Factories must return schema-valid instances. Placement still goes through the
+document-kind command validator; kit validation is not publish authorization.
+
+Use the same trusted definitions in your document kind and server renderer.
+Adding a block to a palette alone does not enable its rendering or publishing.
+The built-in email production adapter currently uses its core email kind; custom
+email target composition and a complete high-level editor component remain work
+in progress.
+
+The package exports `InspectorDrafts`, `builderOutlineLabel`,
+`builderDragAnnouncement`, `updateBuilderCanvas`, `showBuilderBlockActions`,
+`editBuilderText`, `showImageFallbacks`, and `offerBuilderDownload`.
+These are low-level reusable surfaces, not a drop-in complete studio yet.
+The host owns authenticated load/save/render/asset service callbacks.
+`createBlockEditorState` uses validated commands; host applications must actually
+wire it rather than assuming all application mutations already use that state.