1. Fetches the workspace repos via `attemptsApi.getRepos(workspaceId)`
2. Finds the specific repo and passes its `target_branch` to `CreatePRDialog.show()`
This matches the pattern already used by the `GitRebase` action in the same file. Now when you create a PR from the workspaces (ui-new) layout, the base branch will correctly default to the workspace's target branch instead of the main repo's currently checked-out branch.