tests: fix smolvlm _setup_image_processor to use size=1024 for 2x2 tiles
max_image_tiles is not a recognized SmolVLMImageProcessor field and was
silently ignored, leaving the default size=2048 → 4×4=17 tiles.
Use size={"longest_edge": 1024} = 2×512 to produce 2×2+1=5 tiles,
reducing tile work ~3× in splitting and error tests.
Also add per-case timing prints to test_process_interleaved_images_prompts_image_error
(visible with -s) to identify which cases are slow.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>