Remove react/filesystem dev dependency; use file_get_contents for file reading

[Copilot]

react/filesystem ^0.2@dev has never had a stable release, forcing downstream users to set minimum-stability: dev in their composer.json to install this package.

Changes

• composer.json: Removed react/async and react/filesystem dependencies entirely
• PhpCodeParser.php: Replaced the promise-based async file reading with plain file_get_contents(); all reads were already being await()-ed synchronously so there is no behavioral difference

Before:

$filesystem = \React\Filesystem\Factory::create();
foreach ($phpFileArrayChunk as $cacheKey => $path) {
    $phpFilePromises[] = $filesystem->detect($path)->then(/* ... */);
}
$phpFilePromiseResponses = await(all($phpFilePromises));

After:

foreach ($phpFileArray as $cacheKey => $path) {
    $content = \file_get_contents($path);
    // ...
}

[sonarqubecloud]

Quality Gate failed

Failed conditions
B Maintainability Rating on New Code (required ≥ A)

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