Migrate darrow-verification renderer to Python + uv #177

Parent: #168

Outcome

Migrate darrow-verification's assessment renderer to the established Python + uv plugin pattern without changing verification orchestration or result semantics.

Priority

3 of 14 remaining plugins. It is a second small deterministic renderer that can verify the pattern before stateful CLI migrations begin.

Scope

Replace skills/verify-change/scripts/render-assessment with a contained Python helper and a minimal cross-platform host entrypoint where required.

Done criteria

• Preserve the renderer's accepted inputs, exact assessment format, validation messages, and exit statuses.
• Add focused example and generated tests for field validation, multiline content, escaping, ordering, and malformed inputs.
• Register the package in the Python inventory and pass every Establish and enforce repository-wide Python quality standards #172 quality gate independently.
• Prove fresh copied-plugin installation with locked runtime dependencies and no repository or sibling-plugin references.
• Run direct tests and verification skill evals on Linux, macOS, and native Windows.
• Update plugin documentation and both manifests with matching versions.

Migration blueprint

Use the implementation merged in PR #173 as the default blueprint for Python + uv plugin mechanics. Reuse its self-contained package layout, committed uv lock, runtime/development dependency separation, python-packages.txt inventory, Ruff and strict mypy gates, separate 95% line and branch coverage gates, and fresh copied-artifact validation. Extend that pattern with native-Windows fresh-artifact validation where this rollout requires Windows support. Document any plugin-specific deviation explicitly instead of introducing a competing convention.