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_

Start by locating the Pull request canvas and how it currently renders pull request titles, then find the existing operation used to update pull request data. Implement the pencil, input, save, and cancel states with Enter and Escape behavior, and verify that saving persists the renamed title while canceling leaves it unchanged.

索引モデルが issue の本文から書いたものです。