Document why NodeJS is needed to run the tests - #347

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Thanks @dhruvang21, your version reads better. I reworked the section in 3632464 and used your structure:

• A standalone ### Why Node.js is needed section, with "Node.js" spelled correctly.
• It opens with why a PHP suite needs Node.js.
• The Gutenberg steps are numbered in order, starting with the pinned version.
• It ends with your summary sentence.

I kept a few things that your text left out, because hosts need them:

• The server must reach ghcr.io. On a firewalled host, prepare.php fails there.
• The links to changeset 61438 and PHPUnit tests fail: routes.php generated under build/ but tests bootstrap from src/ #292, so readers can check why the files are missing and what the error looks like.
• Core runs PHPUnit after npm run build:dev, with a link to Find ways to reduce the need for NodeJS #244.

I also added that devEngines enforces the npm version, in addition to engine-strict. Could you take another look?

@iarif4u The technical details here are useful, but I think the section could be improved for clarity, flow, and grammatical accuracy. Rather than making several small edits, could we replace the current section with the version suggested in the change? It keeps the technical details while making the explanation easier to follow.

@dhruvang21 Done in 148566c. The section now uses your version, with your sentences. I only added back the facts that your version left out, each as a short clause in your text:

• The build commands (npm install && npm run build) and a link to the Gruntfile.
• Changeset 61438, which removed these files from version control.
• gutenberg.sha in package.json, where the pinned version comes from.
• "the server must be able to connect to ghcr.io". Hosts with an outbound firewall need this.
• The routes.php example from PHPUnit tests fail: routes.php generated under build/ but tests bootstrap from src/ #292, so readers know what the failure looks like.
• Under Versions: devEngines and the EBADDEVENGINES error that npm shows. vairafiq got this error on Node.js 22 in Update test runner Node.js requirement to 24.x hosting-handbook#445.
• Under Extra work: Core's own PHPUnit workflow uses npm run build:dev, and Find ways to reduce the need for NodeJS #244.

I also applied @mindctrl's two heading suggestions. Could you take another look?

#351 is merged, so as agreed I updated the wording in 47af3de. The section now says that prepare.php runs npm install && npm run build:dev, and the "Extra work" note is replaced by a short "Development build" note. It says the development build is the same as in Core's PHPUnit workflow, writes into src/, and skips build/ and minification. No other changes. @mindctrl @ekamran @dhruvang21, since this came after your approvals.