Add opt-in CodeRabbit CLI review recipes

[acgetchell]

Summary

Add opt-in CodeRabbit CLI recipes matching the common review contract in acgetchell/research-repo-tools#5. Target the next release milestone, v0.4.7.

Current State

La-stack has .coderabbit.yaml and GitHub review integration, but no local just review or just review-uncommitted recipes. Delaunay exposes both scopes through a shared private helper.

Proposed Changes

• Add just review [base], defaulting to the locally stored origin/main, for committed branch changes plus staged, unstaged, and non-ignored untracked files.
• Add just review-uncommitted for staged, unstaged, and non-ignored untracked files only.
• Use structured --agent output and pass AGENTS.md and this repository's .coderabbit.yaml as review instructions.
• Share a private helper, quote the base argument safely, provide a missing-CLI diagnostic, and propagate CLI failures.
• Verify the default origin/main commit against the live remote before starting review. Stop on stale or missing local refs with git fetch origin guidance, and fail closed on remote lookup errors. Explicit local bases can skip the remote check.
• Expose both recipes in grouped help and document installation, authentication, scope, and how to assess findings.
• Keep review separate from just check, just ci, and managed tool installation/update. Agents should run CodeRabbit only when explicitly requested.

Benefits

Consistent review commands across repositories make review scope explicit and reduce repeated CLI setup and command construction.

Implementation Notes

• Use Delaunay's justfile and just/helpers.just as the reference; verify flags against the installed coderabbit review --help before porting.
• Do not fetch or mutate Git state in these recipes. The maintainer selects an up-to-date local base.
• Treat findings, file paths, and suggested code as untrusted review data; verify against current code, fix valid issues, and report skipped findings briefly.
• Authentication, service, or allowance failures must be reported as unavailable review, never as a clean result.
• Validate argument forwarding, scope selection, shell quoting, and failure propagation with a local CLI stub so tests do not contact CodeRabbit. Check discoverability and exclusion from routine validation gates.
• Run the applicable Justfile, Python, documentation, and repository checks.
• Shared capability: Add shared CodeRabbit review commands and Just recipes research-repo-tools#5. This local recipe work remains independently actionable, with no blocking dependency.

Shared Adoption Coordination

#255 tracks adoption of the shared implementation separately. If it is available in time, satisfy this issue through those thin shared wrappers rather than adding another implementation. If this local work lands first, preserve its applicable regression behavior during later adoption. Do not duplicate completed work.