fix: ensure sdk version is set before root composer install

[devin-ai-integration]

Fix PHP SDK Publishing Workflow

Problem

The PHP SDK publishing workflow is failing at the "Install root composer dependencies" step because the version field in the PHP SDK's composer.json is empty when Composer tries to resolve dependencies from the root composer.json.

Solution

1. Added a dedicated step to ensure the SDK version is set before installing root dependencies
2. Added more debug logging to help diagnose any future issues
3. Added validation to ensure the version is properly set before proceeding with installation

This fix ensures that the PHP SDK version is always properly set before the root composer.json tries to resolve dependencies, preventing the "Invalid version string" error.

Link to Devin run: https://app.devin.ai/sessions/6407d462e80c47b4b98a7af1e3565247
User: Max Prilutskiy (max@lingo.dev)

[devin-ai-integration]

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