Scheduled automation fails when a non-default branch is checked out locally

Describe the bug

A scheduled repository automation fails when the associated local clone is currently checked out to a branch other than the workflow/default branch. The failure instructs the user to switch the local clone back to the expected branch before rerunning the workflow.

A scheduled automation should not depend on whichever branch happens to be checked out in a mutable local working copy. This makes schedules unexpectedly brittle and allows unrelated local development activity to break them.

Affected version

No response

Steps to reproduce the behavior

1. Configure a scheduled automation for a repository while its workflow/default branch is selected.
2. In the associated local clone, check out a different branch for unrelated work.
3. Allow the scheduled automation to run.
4. Observe that it fails because the workflow/default branch is not currently checked out locally.

Expected behavior

Scheduled automations should run against the configured workflow branch or repository default branch regardless of the local clone's currently checked-out branch. If a local checkout is required, Copilot should use an isolated worktree/clone or safely resolve the configured branch without requiring the user's active working tree to switch branches.

Additional context

The visible error explicitly says the workflow branch is not checked out and asks the user to switch branches in the local clone. Identifying repository, branch, organization, and automation names have been intentionally omitted. The original screenshots contain those details and should not be attached without redaction.

未指定源文件或测试。首先，在本地检出一个非默认分支的情况下复现一次计划自动化，然后跟踪 CLI 对已配置 workflow 或默认分支以及本地工作副本的处理。完成标准是：自动化可以运行，而不要求用户当前的 checkout 切换分支，并且为所报告的场景提供 coverage。