Upgrade darrow-skill-authoring for Python + uv plugin mechanics #175

Parent: #168

Outcome

Upgrade darrow-skill-authoring to support and exemplify the repository's incremental Python + uv plugin-mechanics model. Use this migration to establish the reusable packaging, entrypoint, locking, quality, and native-Windows pattern that later plugin migrations will follow.

Priority

1 of 14 remaining plugins. This goes first because its authoring guidance and inspectors govern the quality of every subsequent plugin migration.

Scope

Migrate the substantial deterministic mechanics currently implemented by inspect-skill and verify-shell-tests where Python materially improves clarity and portability. Retain only genuinely small host-specific shell glue. Preserve every model-facing output, validation rule, refusal, and exit status.

Done criteria

• Record the broader incremental Python + uv adoption decision required by Research Python + uv for shared scripts and native Windows support #168, updating or superseding ADR-0005 without weakening plugin independence.
• Define the canonical contained Python package, uv lock, entrypoint, fresh-install, and native-Windows conventions for plugin helpers.
• Bring migrated code under the repository Python inventory and all quality gates established by Establish and enforce repository-wide Python quality standards #172.
• Update author-agent-skill guidance and validation so future skills can choose Python or small shell glue consistently.
• Preserve inspector and test-discovery behavior with regression coverage for paths, interpreter routing, malformed skills, and failure output.
• Validate the plugin from a fresh copied artifact on Linux, macOS, and native Windows; keep runtime and development dependencies separate.
• Pass direct script tests, skill evals, repository checks, and matching manifest version bumps.

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.