Fix OpenRouter streamed billing reconciliation by replacing the streamed estimated cost with the provider generation metadata total when the final streamed response includes a response id.
Verified with focused OpenRouter tests, full OpenRouter extension tests, formatting/diff checks, autoreview, official OpenRouter generation metadata docs, and a live OpenRouter API stream plus delayed generation lookup. Remaining CI failures were inspected and are unrelated existing failures outside the OpenRouter surface.
Fixes#68066