Allow renaming a pull request name from within the Pull request canvas

### Feature summary

Renaming a PR title from GHC app PR canvas

### What problem are you trying to solve?

I want to be able to rename the pull request directly from the canvas similar to the experience on the Github website.

### Proposed solution

My suggestion:
- Add a pencil icon button
- When the button is clicked change the title to a Input + Save button + Cancel button
- If Saved is clicked, it does the operation then changes back text only
- If Cancel is clicked, it does not trigger any changes and goes back to text only
- When in edit mode, enter key is equivalent to clicking save, ESC key is equivalent to clicking cancel

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_

首先定位 Pull request canvas，了解其中当前如何渲染 pull request 标题，然后找到用于更新 pull request 数据的现有 operation。实现 pencil、input、save 和 cancel 状态，以及 Enter 和 Escape 的行为，并验证保存会持久化重命名后的标题，而取消会使其保持不变。

由索引模型根据 Issue 内容生成。