fix: scope the Playwright server state to a single run

[yeapea]

We hit this on a long browser suite and it took a while to pin down, so here it is with the repro.

AlreadyStartedPlaywrightServer writes the running server's host and port to one path per project:

vendor/pestphp/pest-plugin-browser/.temp/playwright-server.json

Every parallel worker reads it on each visit(). The path has nothing in it that identifies the run, and markAsStopped() unlinks it unconditionally. So if two test processes are going in the same checkout, the second one overwrites the description and then deletes it when it finishes. The first run's workers were already talking to the second run's browser at that point, which is why nothing looks wrong until the file disappears and every remaining test dies with:

file_get_contents(.../.temp/playwright-server.json): Failed to open stream: No such file or directory

For us that was a suite that ran two catalogue sweeps that overlap. 937 cases, 257 passed, then 680 failed in a row, none of them for a reason that had anything to do with what they were testing.

What changed: the state file now carries a run id that the main process mints and exports, so a worker resolves the server of the run it belongs to, and a teardown can only remove its own description. Files from a run that got killed before its teardown are cleaned up after six hours, otherwise they'd just accumulate.

One detail that cost me an afternoon and might be worth knowing: exporting the run id with putenv() alone does not work. Symfony's Process builds the inherited environment as array_intersect_key(getenv(), $_SERVER), so a variable that only exists in getenv() gets dropped before a ParaTest worker ever sees it. It needs $_SERVER and $_ENV too. The fix looked correct and did nothing until I checked that specifically.

I also moved the Port::find() call in ServerManager::playwright() inside the guard. Only the first call creates the server, but every call was finding a fresh port and persisting that one, so from the second call onwards the file described the running server by a port nothing was listening on. In practice the window is small because the second call comes from terminate(), but it's wrong either way.

Three tests in tests/Unit/Playwright/. They fail on 5.x without the source change and pass with it, so they're checking the thing and not the wiring.

Happy to adjust the approach if you'd rather solve it another way. The run id in an environment variable is the least invasive thing I could find that also works for ParaTest workers, but if there's a mechanism in Pest for this that I missed, I'll gladly use it instead.

[Sagmedjo]

We ran into this independently: several test runs in one checkout at the same time (parallel agents and terminals), and the run still going lost its remaining browser tests to file_get_contents(.../.temp/playwright-server.json): Failed to open stream.

Reproduced with two concurrent pest --parallel --processes=3 runs over browser tests in the same checkout: whenever the second run finished first, 2 of 5 tests in the first one failed. With this PR's AlreadyStartedPlaywrightServer (we carry it as a local override until this lands), both runs passed in three rounds out of three.

On your question whether Pest has a mechanism for this: Pest\Plugins\Parallel::setGlobal() / getGlobal() is what TIA and sharding use to hand values from the main process to the ParaTest workers. setGlobal() writes to $_ENV under a PEST_PARALLEL_GLOBAL_ prefix, and Symfony Process builds a child's default environment as $_ENV merged over the filtered getenv(). So it reaches the workers, which matches what you found about putenv() alone. Minting the run id through setGlobal() would replace the hand-rolled export. It might even carry host and port themselves, since the server is persisted during test collection, before the workers start; that would make the file and its stale-file cleanup unnecessary. Your call whether that is worth the larger change.