fix(symfony): make api-platform/test a dev dependency

[soyuka]

Fixes the Guides job, red on main since #8526.

What broke

#8526 added api-platform/test to the require section of src/Symfony/composer.json. That made it reachable from docs/composer.json (which requires api-platform/symfony), where pmu links it as @dev:

api-platform/symfony dev-… requires api-platform/test @dev
  -> api-platform/test dev-… requires phpunit/phpunit ^11.5 || ^12.2
  -> conflicts with root composer.json require (^10)

Dependency resolution fails outright, so the guides job dies at Install project dependencies and nothing downstream runs.

The green/red boundary is a single commit: the guides run on c587c81e0 — which already contained #7887 — was green; the first red one is 515b6f468, exactly the commit that added the require entry. So this is #8526's doing, not the original extraction's.

Why require-dev is the right fix, not bumping docs' phpunit

This is a packaging bug independent of CI: require would pull PHPUnit into every production install of api-platform/symfony.

The precedent is already in the codebase. On 4.4, when api-platform/symfony still shipped the ApiTestCase helpers itself:

"require":     { …no phpunit… }
"require-dev": { "phpunit/phpunit": "^11.5 || ^12.2" }

Test helpers ship in the package; their test-only dependencies stay dev-only. The deprecated shims at ApiPlatform\Symfony\Bundle\Test\* are only ever loaded from test code, so they get the same treatment, plus a suggest entry so users of the deprecated classes know what to install.

symfony/deprecation-contracts deliberately stays in require — the shim files call trigger_deprecation() at file scope in shipped code, so it is a genuine runtime dependency.

Not included

PHPUnit (PHP 8.5) (MongoDB) is also red on main, but it is unrelated and pre-existing — it was merged red in #8491 on 2026-09-02 and was merely masked on main by #7887's bootstrap fatal. UriVariableParameterProviderTest calls recreateSchema() in setUp() while its markTestSkipped() mongodb guards sit inside the test bodies, and tests/Fixtures/TestBundle/Document/Base64UriVariableDummy.php does not exist. Left for a separate change.

https://claude.ai/code/session_01FmRmcWx8J7PS374edGFBdE