Two defects in the image output counter could inflate imageCount for
text-only responses, causing per-image charges instead of token billing:
1. addDataArray counted every element in a top-level "data" array
without checking whether each element contained actual image output
(url/b64_json). Non-image objects in a "data" array are now skipped.
2. addImageOutputItem accepted image_generation.completed items with
no result/b64_json/url, inflating the count. These items are now
filtered the same way as every other item type.
Fixes#3196
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
