Recognize metadata frontmatter field

[kriptoburak]

Summary

• Treat metadata as an ecosystem-common frontmatter field instead of an unknown field.
• Add a nested metadata fixture with public homepage and repository values.
• Update the README test count for the added regression test.

Validation

• git diff --check
• python -m pytest -q
• npx --yes markdown-link-check README.md tests/fixtures/metadata_field.md --quiet

[nbeai]

This looks like a useful false-positive fix. One edge case I would keep in mind: metadata often becomes a marketplace-specific namespace, so it is probably best treated as ecosystem info without requiring skillcheck to understand every nested key. A regression where metadata contains both normal links and an unknown nested namespace would help preserve that boundary.

[kriptoburak]

Added the regression suggested here: the fixture now keeps regular metadata links and an unknown nested marketplace namespace under metadata, and the parser test asserts that nested metadata is preserved. Validation: git diff --check; npx --yes markdown-link-check tests/fixtures/metadata_field.md --quiet; uv run --python /Users/burak/.local/bin/python3.11 --with pytest --with pytest-cov --with pyyaml python -m pytest -q -o addopts= tests/test_v1_2_false_positive_fixes.py.

[moonrunnerkc]

Thanks @kriptoburak, merged! Fixed the README conflict on the way in (set the test count to 833 = main's 832 + your new test). Nice first contribution.