The subjectFilterRequest field requires a nested structure:
{ subject: 'hostFinding', filterRequest: { filters: [...] } }
Previous attempts with flat { filters: [] } or { subject, filters }
caused Ivanti to return 500. The filterRequest wrapper is required.
Also adds docs/ivanti-api-reference.md documenting all known endpoints,
field formats, and the subjectFilterRequest structure so we don't have
to reverse-engineer the Swagger again.
