Failing tests: multi-file upload temp dir and chat backup delete - #29854

Failing tests, no fixes, for Go bugs the desktop e2e release gate found.

Multi-file upload deletes the shared temp dir (go/kbfs/simplefs)

Desktop drag-and-drop puts every dropped file in one temp dir from SimpleFSMakeTempDirForUpload. When the first upload finishes, waitForCopy removes its file's parent dir (dirToDelete) — the shared dir — so the other dropped files are gone before or while they upload.

• TestUploadSharedTempDirMultipleFiles: two files in one temp dir, uploaded one after the other. Fails with "finishing the first upload removed the second file from the shared temp dir".
• TestUploadSharedTempDirMultipleFilesConcurrent: a file, a 100-file folder and another file started back to back, as a drop does. Fails with "upload to /private/jdoe/folder: file or folder does not exist". It depends on the first upload finishing before the folder copy does, which held in 50/50 runs.

Both also require the shared dir to be removed once every upload from it is done, so a fix can't pass by leaking the copied files.

Chat backup Delete leaves output behind (go/chat)

• TestArchiveRegistryDeleteRemovesOutputOfUnwindingJob: ChatArchiveRegistry.Delete cancels a running job and starts os.RemoveAll on its output without waiting for the job to stop. The job, still unwinding, recreates its folders and opens chat.txt after the removal. Fails with "cancelled job wrote into .../kbchat-out after Delete removed it". It also requires the deleted job to stay out of the registry. (Pause has the same no-wait shape; not tested here.)
• TestArchiveRegistryDeleteRemovesCompressedOutput: a finished job made with Compress: true leaves <output>.tar.gzip, and Delete(jobID, true) removes only the directory path. Fails with "Delete left the compressed output .../kbchat-out.tar.gzip behind".

Evidence

Each test fails 3/3 on master with -race, and passes under a stand-in fix (not included). gofmt, go vet and golangci-lint --new-from-rev origin/master are clean.