OpenRouter (_generate_via_chat, _generate_via_image_api) and OpenAI gpt-image
called record_token_usage only after image extraction and save succeeded. A
token-billed 200 that returned text but no image (the "returned no image"
fallback case), an empty `data` list, or a failed save therefore consumed
billed tokens that never reached session_model_usage; on the fallback chain
only the fallback model's tokens were recorded.
Move the call to immediately after a successful post_json / SDK call, before
extraction/save, in all three paths. One call per HTTP success, so no double
count; failure responses (non-2xx, timeouts) still record nothing because
there is no body to read usage from.
Tests: the parametrized invariant in test_openrouter_compat_provider gains the
no-image-with-usage case for both surfaces (result is `empty_response`, one row
still recorded); the OpenAI test is parametrized on has_image the same way.
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