feat(review): introduce the review protocol and code-review skill

[pentaxis93]

Summary

• Introduces review as a source C-2 workflow contract that consumes change-proposal and emits exactly one typed review outcome.
• Adds the code-review skill as the cognitive review discipline without forge-specific tooling.
• Replaces the old review-findings runtime artifact surface with change-approved / change-needs-revision schemas, fixtures, manifest registration, and conformance coverage.

Changes

• Registers review outcome artifact types, [[outcome_types]], the review operation handle, and a required-choice review-disposition output group in manifest.toml.
• Adds workflow-contracts/review.toml and skills/code-review/SKILL.md.
• Updates schema docs, the Step 2 design note, and ADR-0002 supersession guidance so current authoring points at typed review outcomes while ADR history remains intact.
• Preserves the invalid-shared-record-type-outcomes.toml guard as the negative counterpart to the new valid review contract.

GitHub Issue(s)

Closes #331

Test plan

• python -m tooling.conformance
• python -m unittest discover -s tests
• git diff --check