Add spec tests for cfdp-eio and osv, rewrite osv parser with jsont
cfdp-eio tests (24 new, 61 total):
- Wire framing: length-prefix encode/decode round-trips (empty, small,
1024, 65535 byte payloads), error cases (truncated, negative, overlarge)
- PDU round-trip through framing for all CCSDS 727.0-B-5 PDU types:
Metadata, FileData, EOF, Finished, ACK, NAK, KeepAlive, Prompt
- Multi-PDU transfer sequence (Metadata->Data->EOF stream)
- Wire format: verify 4-byte BE length prefix, PDU version field = 001
osv: rewrite JSON parser from hand-rolled to jsont codecs (OSV Schema
v1.6). Defines typed codecs for vulnerability, severity, reference,
affected range, and batch response types.
osv tests (20 new):
- CVSS v3.1 severity boundaries from FIRST.org spec (0.0-10.0)
- Real CVE scores: Log4Shell, Heartbleed, Meltdown, Dirty Pipe
- JSON parsing with actual OSV API response format: minimal, with
severity, aliases, multiple, npm/RustSec/PyPI advisories
- Filtering by severity, CVE ID extraction, has_fix detection