feat: defer remote branch creation until first commit (#244)

* feat: defer remote branch creation until first commit

- For commit signing: branches are created remotely by github-file-ops-server on first commit
- For non-signing: branches are created locally with 'git checkout -b' and pushed when needed
- Consolidated duplicate branch creation logic in github-file-ops-server into a shared helper function
- Claude is unaware of these implementation details and simply sees it's on the correct branch
- No branch links are shown in initial comments since branches don't exist remotely yet

* fix: prevent broken branch links in final comment update

- Check if branch exists remotely before adding branch link
- Only add branch links for branches that actually exist on GitHub
- Add test coverage for non-existent remote branches
- Fixes issue where users would see broken branch links for local-only branches

* fix: don't show branch name in comment header when branch doesn't exist remotely

- Only pass branchName to updateCommentBody when branchLink exists
- Prevents showing branch names for branches that only exist locally
- Add test to verify branch name is not shown when branch doesn't exist

* tmp

src/entrypoints/update-comment-link.ts

@@ -201,7 +201,7 @@ async function run() {
       jobUrl,
       branchLink,
       prLink,
-      branchName: shouldDeleteBranch ? undefined : claudeBranch,
+      branchName: shouldDeleteBranch || !branchLink ? undefined : claudeBranch,
       triggerUsername,
       errorDetails,
     };