[Feature] Faster way to start new workspace + worktree from GitHub issue or PR

[rogersmj]

I often want to align each workspace with a GitHub issue or PR, and doing this in T3 Code is a process I find tedious.

Starting a new session/worktree from a GitHub issue takes way too many clicks/commands, and seems to require initiating a chat just to get a workspace. Currently, the process is:

1. New thread
2. Select project (if you didn't do step 1 from inside the current project)
3. Select "new worktree" from the dropdown at the bottom left of the chat input
4. Select "From origin/main" and then search for the issue number/PR you want.
5. If it's a PR, another dialog pops up, "Checkout Pull Request". On this you have to click Worktree again (even though I had already selected Worktree on the chat)
6. Type your prompt, click to send -- only now is the workspace/worktree created

In Orca, by comparison, it's basically two steps:

1. Click new session button next to the project
2. Type to search -- auto-searches github issues/PRs that you can select as you type, or just give the new workspace a name.

That's it. Now you have a workspace (before you've sent a chat). See screenshot below for the "new workspace" dialog Orca has:

(Orca also makes this easy from a Tasks page that lists all your GitHub issues, and you can one-click them for a new workspace, but that's a separate feature.)

Related in the realm of creating new workspaces/worktrees: #8334, #6978