Clarify plugin authoring and external dev workflow

packages/plugins/examples/plugin-authoring-smoke-example/README.md

@@ -0,0 +1,23 @@
+# Plugin Authoring Smoke Example
+
+A Paperclip plugin
+
+## Development
+
+```bash
+pnpm install
+pnpm dev            # watch builds
+pnpm dev:ui         # local dev server with hot-reload events
+pnpm test
+```
+
+## Install Into Paperclip
+
+```bash
+pnpm paperclipai plugin install ./
+```
+
+## Build Options
+
+- `pnpm build` uses esbuild presets from `@paperclipai/plugin-sdk/bundlers`.
+- `pnpm build:rollup` uses rollup presets from the same SDK.