judge: add ADR link integrity check

[thehanslevi]

Summary

• add judge.py check-links to verify line-start @ADR source tags point at existing ADR records
• report docs/decisions/NNNN-*.md files with no inbound source tag as orphan warnings
• add JSON/text CLI output and regression coverage for valid, dangling, orphaned, gitignored, and Markdown-example cases

Addresses #42.

Validation

• python3 -m py_compile scripts/judge.py tests/test_judge.py
• python3 scripts/judge.py check-links . --json
• /tmp/codex-proof-pr-gen-adr-venv/bin/python -m pytest tests/test_judge.py -q (75 passed)
• /tmp/codex-proof-pr-gen-adr-venv/bin/python -m pytest -q (192 passed, 1 xfailed)
• git diff --check

Notes

• Markdown files are excluded from live tag scanning so fenced documentation examples and ADR files are not treated as source tags. ADR records are still discovered under any docs/decisions directory.