The RustSec advisory-db uses .md files with TOML in a fenced code block,
not plain .toml files. The parser now extracts the TOML block from markdown.
Also fixes:
- --limit now means "collect up to N enriched entries" instead of
"take first N candidates", so it keeps scanning until enough are found
- Suppressed dead_code warnings on Issue variant and deserialization-only fields
- Updated test fixtures to match the .md format
https://claude.ai/code/session_01AeNG3herWfKhos9uZVUY5d