When the Docker API receives markdown_generator as JSON with "options"
instead of "params", from_serializable_dict silently passes the raw
dict through. This later crashes with a confusing "'dict' object has
no attribute 'generate_markdown'" deep in the crawl pipeline.
Add type validation for markdown_generator in CrawlerRunConfig.__init__
(matching existing extraction_strategy/chunking_strategy validation).
When a dict slips through, the error now clearly states:
- What type was expected vs received
- That "params" is the required key (not "options")
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
