test: add adversarial tests for edge cases and malformed data

Add 185 adversarial tests covering edge cases: zero IDs bypassing
truthiness guards, malformed API responses, missing/None fields in
transforms, empty Origins arrays, whitespace-only API keys, and
Pydantic model coercion boundaries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: franccesco