Creating a Review document with save to project option

### Describe the feature or problem you'd like to solve

Similar to the /research (-> 'report') and /plan (-> 'plan') slash commands executing /review should also generate a standard output document.

### Proposed solution

Would provide a harmonized behavior for all three agents and a useful output for the /review command.

### Example prompts or workflows

```/review the spec @my_spec``` should result in an output document e.g. named "Review.md".
Similar for review code snippets or (implementation) plans.

### Additional context

_No response_

Start by comparing how the /research and /plan slash commands generate and save their standard output documents. Implement matching behavior for /review, including the example spec, code-snippet, and implementation-plan workflows, and verify that the result is saved as a document named Review.md.

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