[CLI] Fix __dirname not defined error in intl extension

[brandonpayton]

Motivation for the change, related issues

Running npx @wp-playground/cli server --debug currently fails for v3.0.38.

Unhandled rejection: ReferenceError: __dirname is not defined
    at withIntl (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/node/index.js:485:20)
    at async loadNodeRuntime (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/node/index.js:611:25)
    at async Object.createPhpRuntime (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@wp-playground/cli/worker-thread-v1.js:138:48)
    at async t (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@wp-playground/wordpress/index.js:451:15)
    at async PHPProcessManager.phpFactory (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/universal/index.js:2559:21)
    at async PHPProcessManager.doSpawn (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/universal/index.js:2363:17)
    at async PHPProcessManager.getPrimaryPhp (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/universal/index.js:2289:135)
    at async PHPRequestHandler.getPrimaryPhp (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@php-wasm/universal/index.js:2585:12)
    at async L (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@wp-playground/wordpress/index.js:384:13)
    at async V (file:///Users/brandon/.npm/_npx/8ab79f7a2a3f35a4/node_modules/@wp-playground/wordpress/index.js:380:10)

I think our tests for built npm packages should have caught this before merging, so I would like to look into that before merging this fix.

cc @mho22

Implementation details

Use conditional logic to determine the module directory: prefer __dirname when available (CommonJS), fall back to import.meta.dirname (ESM). Also switch to path.join for more robust path construction.

Testing Instructions (or ideally a Blueprint)

• CI

[brandonpayton]

In addition to fix the missing __dirname bug, this PR switches from string concat to explicit path concat.

[brandonpayton]

I think our tests for built npm packages should have caught this before merging, so I would like to look into that before merging this fix.

Confirmed. This issue was introduced by 74446e7. The tests on that commit encountered the error but somehow did not fail the CI job:
https://github.com/WordPress/wordpress-playground/actions/runs/20741861135/job/59550114727#step:4:1869

Looking into it.

[brandonpayton]

Our ES module tests for built NPM packages did not consider timeouts to be failures. That should be fixed now.

[brandonpayton]

Nice! The built package tests are failing due to the missing __dirname bug here:
https://github.com/WordPress/wordpress-playground/actions/runs/20764816212/job/59628496577#step:4:2608

Now that the __dirname fix is restored, we can merge this once the latest CI tests pass.

I have to go AFK shortly and will wait until I am back in 3-4 hours to merge and publish new NPM packages. That way, there is opportunity to confirm all is well with the latest version before moving on to other things.

To others on the team, please feel free to merge and publish before then. The latest published version of Playground CLI is currently broken.

[mho22]

@brandonpayton Thank you!