refactor: improve error message when Node version check fails

[ulises-jeremias]

Context

Old Node version error is generic: "Node.js version X is not supported"

Task

Improve to: show required vs detected version + upgrade instructions (fnm, nvm, manual).

Files to modify

• packages/create-node-app-core/index.ts — checkNodeVersion()

Verification

• Test with older Node version via fnm/nvm

Steps

1. Improve to: show required vs detected version + upgrade instructions (fnm, nvm, manual).
2. packages/create-node-app-core/index.ts — checkNodeVersion()
3. Test with older Node version via fnm/nvm

Acceptance criteria

• Test with older Node version via fnm/nvm

Files

• packages/create-node-app-core/index.ts — checkNodeVersion()

Verification

• Test with older Node version via fnm/nvm

How to verify

• Test with older Node version via fnm/nvm

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Original issue text

Description

Old Node version error is generic: "Node.js version X is not supported"

Task

Improve to: show required vs detected version + upgrade instructions (fnm, nvm, manual).

Files to modify

• packages/create-node-app-core/index.ts — checkNodeVersion()

Verification

• Test with older Node version via fnm/nvm