block_ads is a browser-engine parameter (used by PlayWright/Camoufox
fetchers for ad-domain blocking) and is not recognised by curl_cffi's
Session.request(). When the CLI's --ai-targeted flag sets block_ads=True,
_merge_request_args forwards it unfiltered, causing:
TypeError: Session.request() got an unexpected keyword argument 'block_ads'
Add block_ads to the skip_keys set so it is stripped before the dict
reaches Session.request(), consistent with existing entries for
extra_headers and google_search.
Fixes#247
voidborne-d