stash CLI help banners and "Next steps" panel hard-code npx regardless of runner

[coderdan]

Symptom

Running the CLI via any non-npx runner shows examples and suggested commands using npx @cipherstash/cli regardless of how the user invoked it:

$ bunx @cipherstash/cli --help
Usage: npx @cipherstash/cli <command> [options]   ← should be `bunx`
Examples:
  npx @cipherstash/cli init                       ← copy-pasting these fails
  npx @cipherstash/cli auth login                  if the user doesn't have npm
  ...

$ pnpm dlx @cipherstash/cli auth --help
Usage: npx @cipherstash/cli auth <command> [options]   ← should be `pnpm dlx`

$ bunx @cipherstash/cli db install
... installation succeeds ...
┌  What next
│
│  1. Wire up encrypt/decrypt with the wizard (AI-guided, automated):
│       npx @cipherstash/wizard                   ← should be `bunx @cipherstash/wizard`
│
│  2. Or use the client directly from @cipherstash/stack:
│       import { Encryption } from '@cipherstash/stack'
└

The requireStack hint shown when @cipherstash/stack isn't installed (e.g. running db push on a fresh project) similarly suggests npm install and npx @cipherstash/cli init regardless of runner.

Affected versions

@cipherstash/cli 0.10.x and earlier. The DB-command intros and warnings were addressed in a separate PR; the help banners and the wizard "Next steps" reference remain.

Fix

#379 already shipped runnerCommand(pm, ref) and detectPackageManager(). Sweep the remaining places (top-level HELP, auth HELP, printNextSteps in db install, the requireStack hint) to use them.