Associate branch with PR metadata even when branch is already checked out

When a user is already on the same branch as a PR and clicks "check out PR",
fetchAndCheckout returns early without calling associateBranchWithPullRequest.
This causes the review manager to report "No matching pull request metadata
found" and the PR comments/review UI never loads.

Fix: call associateBranchWithPullRequest before the early return.

Agent-Logs-Url: https://github.com/microsoft/vscode-pull-request-github/sessions/a73abfa2-1150-43fb-a262-a3a0d34a19c3

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/github/pullRequestGitHelper.ts

@@ -125,6 +125,7 @@ export class PullRequestGitHelper {
 			// Make sure we aren't already on this branch
 			if (repository.state.HEAD?.name === branch.name) {
 				Logger.appendLine(`Tried to checkout ${localBranchName}, but branch is already checked out.`, PullRequestGitHelper.ID);
+				await PullRequestGitHelper.associateBranchWithPullRequest(repository, pullRequest, localBranchName);
 				return;
 			}