Conduct PR reviews from within app

### Feature summary

_No response_

### What problem are you trying to solve?

The Inbox page is a nice touch, and seems to be one reason this app might be worth using over VS Code agents (see other issue which points out the clear overlap of these two products, which is confusing given the common parent company). However, I can't comment on the PR diffs currently, which is a bit weird.

Somewhat unrelated, but can anyone explain how the PRs in this app load so much faster than the github website? 🤔

### Proposed solution

_No response_

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_

Comece pela página Inbox existente e pela experiência atual de carregamento de pull requests no app; em seguida, compare como os diffs de pull request são apresentados no site do GitHub. O issue não identifica arquivos de implementação nem testes. Está concluído quando os usuários puderem revisar diffs de pull request e comentar neles dentro do app.

Escrita pelo modelo de indexação a partir do texto da issue.