Rename /review command to avoid plugin namespace collision

[spallen]

Problem

The CodeRabbit plugin registers a /review slash command in Claude Code. This is too generic and collides with other plugins that also register /review — specifically the Sanity Agent Toolkit plugin.

When a user has both plugins installed, typing /review shows two ambiguous options:

/review    (sanity-plugin) Review code for Sanity best practices and common issues.
/review    Review a pull request

There is no way for the user to disambiguate without using the fully-qualified coderabbit:review form, which most users don't know about.

Suggested fix

Rename commands/review.md to something namespaced, e.g.:

• commands/coderabbit-review.md → /coderabbit-review
• commands/cr-review.md → /cr-review

This is the only command the plugin ships, so there's no backwards-compatibility concern with other CodeRabbit commands.

Context

• Claude Code plugin marketplace plugins share a flat slash-command namespace
• /review is an extremely common verb — any code-review, security-review, or best-practices plugin is likely to claim it
• The Sanity plugin has the same issue and is being notified separately