Plugin marketplace cache ignores  ref  when shared across projects with different branches

Describe the bug

When two projects reference the same git-based marketplace source but pin different  ref  values (branches) in  .github/copilot/settings.json 's  extraKnownMarketplaces , Copilot CLI reuses a single on-disk cache checkout keyed only by the source URL/path — not by  ref . Opening a project that expects  branch1  does not re-checkout the cache to  branch1  if it was last left on  branch2  by another project.

Affected version

Copilot CLI 1.0.80

Steps to reproduce the behavior

1. Create marketplace repo with  branch1  and  branch2 , differing plugin content.
2. Project A's  .github/copilot/settings.json  sets  extraKnownMarketplaces..source.ref = "branch2" . Open Copilot CLI there — cache clones/checks out  branch2 .
3. Project B (different repo) sets  ref = "branch1"  for the same marketplace source URL. Open Copilot CLI there.
4. Expected: cache checks out  branch1  before loading plugins for Project B.
5. Actual: cache in  %LOCALAPPDATA%\copilot\marketplaces<hash-of-source>  remains on  branch2 ; Project B silently loads branch2's plugins instead of branch1's.

Expected behavior

When a project's  .github/copilot/settings.json  specifies a  ref  (branch/tag/commit) for an  extraKnownMarketplaces  entry, Copilot CLI should ensure the local cache reflects that exact  ref  before loading plugins for that session — regardless of what  ref  was last checked out there by a different project sharing the same source URL.

Additional context

Suggested fix (from copilot lol): Include  ref  in the cache key/path, or verify+checkout the requested  ref  on every load regardless of cache state.

使用 .github/copilot/settings.json 重现两个项目的情况，将共享 git 源固定到 branch1 和 branch2，然后检查 %LOCALAPPDATA%\copilot\marketplaces<hash-of-source> 下的 checkout。完成标准是：无论之前哪个项目使用过缓存，每个项目都能从其请求的 ref 加载插件，并且为共享缓存场景提供回归覆盖。