LangFactory detects the language on every call, even when the adapter is cached #654

Problem

Quantum\Lang\Factories\LangFactory::resolve() detects the language on every call, even when the adapter is already cached, and a few details around adapter creation are redundant.

1. detectLanguage() runs on every resolve(), before the cache is checked. _t() and current_lang() go through LangFactory::get(), so every translation repeats the query-parameter, URL-segment and Accept-Language checks and then throws the result away: the detected language is only used when the adapter is first created. It can also throw LangException::misconfiguredDefaultConfig() when an adapter is already cached (no language detected and no lang.default_locale).
2. The cache ignores a later language. The adapter is cached by name and keeps the language it was created with. For the web app this is by design: PrepareRequestStage calls LangFactory::get() once per request, which fixes the language for that app context, and Lang::setLang() changes it. This is not documented in the code.
3. The factory builds an HttpClient the adapters already create. createInstance() uses new $adapterClass($lang, $langConfig) for the file adapter and new $adapterClass($lang, $langConfig, new HttpClient()) for the others, but DeepLAdapter and GoogleTranslateAdapter take ?HttpClient $httpClient = null and default to new HttpClient() themselves.

Proposal (non-breaking)

• In LangFactory::resolve(), return the cached instance before calling detectLanguage(). Behaviour for callers does not change: today the detected value is already ignored once the adapter exists.
• Document on resolve() that the language is fixed when the adapter is first created, and changes with Lang::setLang().
• In createInstance(), build all three adapters with new $adapterClass($lang, $langConfig) and drop the HttpClient import.

No signature changes.

Tests

• New, must fail without the fix: after one LangFactory::get(), remove lang.default_locale and the detection sources, call LangFactory::get() again and assert the same instance is returned and nothing throws (today the second call throws).
• New: after the first call, change the lang query parameter and assert the second call still returns the instance with the first language and does not read the request again.
• The existing LangFactoryTest cases for DeepL and Google keep passing without the explicit HttpClient.

Not in this ticket (3.2.0)

The language is also stored twice at creation: the adapter constructor sets $this->lang, then Lang::__construct() calls setLang(), which calls $adapter->setLang() with the same value. It is harmless, and removing it means changing the adapter constructors to take only the config, which is a public signature change. To be handled with a 3.2.0 or later change to the adapter factories.

Acceptance

• A cached adapter is returned without any language detection.
• composer cs:check, composer phpstan and vendor/bin/phpunit tests/Unit/Lang pass.
• CHANGELOG.md entry.