Search file contents across knowledge bases visible to the current API key.

Uses the current API key's permissions. Check GET /capabilities for availability. Searches indexed content across accessible KBs and collapses matches to one result per file. Pagination starts at page=0. Increase page while pagination.has_more is true; do not infer completion from an estimated total. The q parameter searches content, unlike q on the uploaded-file list, which filters filenames. Returned page is zero-based when present.