Migrate darrow-review mechanics to Python + uv #182

Parent: #168

Outcome

Migrate darrow-review's review routing, scope, provider, report, and result mechanics to Python + uv while preserving independent read-only review behavior.

Priority

8 of 14 remaining plugins. Its large parsing and subprocess surface should follow the Git migration pattern it consumes conceptually.

Scope

Migrate the substantial commands under bin/ while retaining external reviewer CLIs as provider boundaries and leaving review judgment in the skill/reviewer.

Done criteria

• Preserve all commands, validated TSV formats, scope binding, route selection, report/result semantics, diagnostics, and exit codes.
• Keep the plugin read-only against reviewed repositories and retain original/prior/current candidate binding across verification flows.
• Use safe argument-vector subprocesses and cross-platform paths, encoding, temporary files, cancellation, and provider discovery.
• Add deterministic tests for routing, quoted inputs, malformed records, context assembly, provider failures, and repair verification.
• Register and lock the package and pass all strict Python quality gates.
• Validate fresh copied-plugin execution on Linux, macOS, and native Windows with provider boundaries mocked or explicitly provisioned.
• Keep review eval suites passing and update specs, docs, and matching manifest 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.