feat(subagent-review): converge iterative reviews

[i9wa4]

Summary

• Define guardian-owned finding convergence, invalid-packet quarantine, and reviewer/dispatcher boundaries in skills/subagent-review/SKILL.md.
• Add blind-review packet and normal/blind Historian contracts in skills/subagent-review/references/review-topology.md, nix/home-manager/agents/subagents/reviewer-historian.md, and skills/dotfiles/references/review-output-contract.md.
• Add positive and negative trigger coverage for review waves and dispatcher fan-out, plus Guardian/critic ledger guidance in skills/dotfiles/references/prompt-blocks.md.

Verification

• git diff --check
• Waza readiness, trigger evaluations, frontmatter/private-content validation
• Repository pre-commit checks and nix run .#check

Closes #301