Extend CompletionParams with optional images[] and documents[] so the
provider clients can carry an uploaded lab-report photo or PDF. Anthropic
folds image and native document blocks into the user turn; OpenAI and the
local OpenAI-compatible client fold image_url blocks. Text-only callers are
untouched. Add supportsVisionForConfig / supportsPdfForProvider and an
ocrExtract budget for the Lab-OCR ingestion path.