CLI runs on Node 20+: npx storebound (bunx keeps working)

- cli/lib/rt.ts: the runtime layer on node: modules (spawn / spawnSync with Bun's defaults, exit codes and
  "Executable not found", which with PATHEXT, sleep, serve, Glob, hasher, gunzip, stdin, SQLite, packageRoot,
  config imports with a type-stripping fallback for Node 20); every Bun.* use in cli/ goes through it
- tools/gen-embedded.ts -> cli/lib/embedded.ts: templates/, cli/shots/*.html and Play's Data safety form embedded
  (replaces Bun text imports; the bundle and the compiled sidecar carry them), checked fresh by bun run ci
- package.json: bin dist/storebound.mjs (Node ESM bundle, tools/build-node.ts, prepack), engines node >=20
- bun run ci: node bundle + node smoke (real node: --version, help, check same as Bun, scan, release plan --help,
  init, MCP handshake + tool call); Forgejo CI sets up Node 20; tests/node-compat.test.ts guards cli/
- install writes npx MCP commands when run with Node; bin/storebound falls back to Node
- docs: npx storebound init (Node 20+) or bunx storebound init

cli/lib/upsert.ts

@@ -13,6 +13,7 @@
 import { existsSync, mkdirSync, readFileSync, renameSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { log, warn } from './log';
+import * as rt from './rt';
 
 /** A write whose outcome is unknown: it may or may not have been applied (timeout, connection reset, 5xx answer to a
  *  POST). The API clients throw this instead of retrying such a request. */
@@ -58,7 +59,7 @@ export function retrySafe(method: string, path: string): boolean {
 }
 
 /** Waits between re-checks (STOREBOUND_UPSERT_WAIT_MS; the test preload sets 0). */
-export const upsertTiming = { waitMs: Number(process.env.STOREBOUND_UPSERT_WAIT_MS ?? 3000), tries: 4, sleep: (ms: number): Promise<void> => (ms > 0 ? Bun.sleep(ms) : Promise.resolve()) };
+export const upsertTiming = { waitMs: Number(process.env.STOREBOUND_UPSERT_WAIT_MS ?? 3000), tries: 4, sleep: (ms: number): Promise<void> => (ms > 0 ? rt.sleep(ms) : Promise.resolve()) };
 
 export interface CreateOnce<T> {
   /** what is being created, for log lines and errors: `in-app purchase com.example.gems` */