Opening Issue editor should be instantaneous

[joaomoreno]

Testing #6832

When clicking on an issue, there's a split second where it feels we're downloading something from the web until the editor is open. The editor should open instantly and whatever loading needs to happen, should happen as part of the editor loading phase.

Screen.Recording.2025-04-29.at.11.14.40.mov

[alexr00]

To verify:

• install the latest pre-release
• Open a PR description from the Pull Requests view
• Open another PR description from the Pull Requests view
• verify that the webview shows "loading..." right away and then a moment later shows the new PR