nx.json should support parallel as a percentage to be consistent with cli arg

[Tungsten78]

Current Behavior

The docs for nx.json constrain parallel as a number.

This is inconsistent with Run Tasks in Parallel which additionally supports a percentage.

Expected Behavior

For consistency and flexibility, support both number and percentage.

The percentage is desirable in order to handle various host environments - our dev systems have way more cores than our hosted azure agents (2 cores).

GitHub Repo

No response

Steps to Reproduce

1. In nx.json, set "parallel": "50%"
2. nx run-many -t build

Expected:

• see parallel task count equal to half the available cores

Actual:

• failure with error
  -| NX The "setMaxListeners" argument must be of type number. Received type string ('50%10')

Nx Report

Node           : 22.16.0
OS             : win32-x64
Native Target  : x86_64-windows
npm            : 10.5.0

nx (global)            : 20.0.6
nx                     : 20.8.2
@nx/js                 : 20.8.2
@nx/jest               : 20.8.2
@nx/eslint             : 20.8.2
@nx/workspace          : 20.8.2
@nx/angular            : 20.8.2
@nx/cypress            : 20.8.2
@nx/devkit             : 20.8.2
@nx/eslint-plugin      : 20.8.2
@nx/module-federation  : 20.8.2
@nx/plugin             : 20.8.2
@nx/rspack             : 20.8.2
@nx/web                : 20.8.2
@nx/webpack            : 20.8.2
typescript             : 5.7.3
---------------------------------------

Failure Logs

Package Manager Version

No response

Operating System

• macOS
• Linux
• Windows
• Other (Please specify)

Additional Information

No response