fly launch: JS package manager should be autodetected

[benwaffle]

Describe the bug When I run fly launch in a node.js app, it should autodetect whether I've used pnpm or yarn instead of npm when installing @flydotio/dockerfile@latest.

• Operating system: macOS 15.2
• fly version: v0.3.75

** Command output: **

installing: npm install @flydotio/dockerfile@latest --save-dev
npm error code EUNSUPPORTEDPROTOCOL
npm error Unsupported URL Type "workspace:": workspace:*
npm error A complete log of this run can be found in: /Users/ben/.npm/_logs/2025-02-07T06_27_33_900Z-debug-0.log
Error: failed to install @flydotio/dockerfile: exit status 1

(this comes from a local package reference from turborepo)