Additional work for AI 1.2 ecosystem. Aligns with stream iterator, usage...

Tyler Brown Cifu Shusterrequested to merge
issue/ai_provider_openrouter-3627909:3627909-reasoning-effort into 1.0.x

Additional work for AI 1.2 ecosystem. Aligns with stream iterator, usage propagation, and input normalization. Passes phpstan and other checks.

Closes #3627909

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