Evaluate command-triggered Claude Deep Review workflow

[justin808]

Context

shakacode/shakastack-com#15 is adding the baseline Claude workflows plus a separate command-triggered Claude Deep Review workflow.

The idea is to keep the normal always-on review workflow explicit and deterministic, while still allowing maintainers to test Anthropic's default plugin-based review path on demand by commenting /claude-deep-review on a PR.

Proposal

Consider adding the same optional workflow here:

• trigger on PR comments containing /claude-deep-review
• use plugin_marketplaces: "https://github.com/anthropics/claude-code.git"
• use plugins: "code-review@claude-code-plugins"
• use prompt: "/code-review:code-review ${{ github.repository }}/pull/${{ github.event.issue.number }}"

This should be treated as an experiment, not a required gate, until we know whether the plugin review is consistently useful and reliably posts comments.

Acceptance criteria

• Add an opt-in Claude plugin deep-review workflow triggered by /claude-deep-review in PR comments.
• Keep the existing deterministic Claude review workflow unchanged.
• Document any repo-specific differences if the workflow cannot match shakastack-com exactly.