[Feature Request] - Show Full PR Details

### Feature summary

The PR Canvas should show more details about the PR.

### What problem are you trying to solve?

The PR canvas currently only shows comments and status. I would like if I could see everything that you can see on the Web UI, including adding, deleting, or updating:

- commit history
- reviewers
- assignees
- labels
- milestones
- projects
- etc

### Proposed solution

Mimic the Web UI’s displayed information for PRs.

### Workflow impact

Users will be able to see more about their PRs, and take more actions from inside the app.

### Installation context

Installed v0.2.24 on Arch Linux

### Additional context

I am happy to help / contribute if you allow that, just let me know / assign me an issue. I’d love to help.

Start by locating the PR Canvas and reviewing how it currently displays comments and status. Compare that scope with the Web UI details and actions listed in the issue; done would require a defined, implemented subset of those PR details and actions, with its boundaries agreed.

索引モデルが issue の本文から書いたものです。