- Extract _optimize_images() helper to eliminate duplicate
optimization code (was duplicated between initial pass and
quality-reduction fallback)
- Move quality-reduction estimate to only apply when NOT chunking
(each chunk fits the image limit by definition)
- Fix _merge_chunk_results to return 'chunk_count' instead of 'chunks'
for consistency with plugin.py
- Simplify plugin.py: analysis.get('chunk_count', 1) instead of
fallback chain
- Document that Kilo API gateway is incompatible with AsyncOpenAI
image format (probe returns 0)