nopy: add create-cube command scaffolding a cube from bundled templates

Gathers id, name and directory from flags or prompts (only what the flags
do not supply), then writes manifest.mjs + deploy.py from templates under
src/templates/cube. Templates are named *.example.* so the template
directory itself can never match the loader's manifest+deploy pair rule.

The scaffold refuses a directory that already holds cube files by the
loader's own patterns, checks the id against the loaded cube set (best
effort, exempting the target directory so --force re-scaffolds work), and
warns when the target lands outside every configured cube directory.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ApuW1MMGK2pUQ9mTVRTxc5

packages/nopy/src/templates/cube/manifest.example.mjs

@@ -0,0 +1,15 @@
+import { Manifest } from '@bitsquare/nopy-cubes';
+import { z } from 'zod';
+
+export default Manifest({
+  id: '__CUBE_ID__',
+  name: '__CUBE_NAME__',
+  // dependencies: () => ['apt:essentials'],  // cubes to deploy first
+  // secrets: ['API_TOKEN'],                  // schema keys to mask and never persist
+  schema: z.object({
+    GREETING: z
+      .string()
+      .describe('Message the deploy prints on the host')
+      .default('hello from __CUBE_ID__'),
+  }),
+});