add back about exist pgpm workspace

Author: theothersideofgod

.agents/skills/constructive-starter-kits/references/nextjs-app.md

@@ -69,6 +69,21 @@ pgpm init \
   --moduleName <module-name>
 ```
 
+**Required arguments for existing workspace :**
+
+| Argument | Description |
+|----------|-------------|
+| `--moduleName` | Module/package name for the new boilerplate |
+
+This creates the module at `packages/<module-name>/` within your existing workspace. The workspace-level arguments (`--name`, `--fullName`, `--email`, etc.) are **not needed** since the workspace already exists.
+
+> **Note:** You must run this from the workspace root or a valid `packages/` subdirectory. If you are not inside a pnpm workspace, pgpm will error with "Not inside a PNPM workspace." Use the `-w` flag (see above) to create a new workspace and module together.
+
+> **Interactive mode (for humans):**
+> ```bash
+> pgpm init --repo constructive-io/sandbox-templates --template nextjs/constructive-app
+> ```
+
 ### 2. Install Dependencies
 
 ```bash