fix(server): stop background status fetches after repeated timeouts

[macodev00]

What Changed

Background upstream refresh stops polling a remote after three consecutive git fetch timeouts. Silent credential-helper success is unchanged. An explicit pull, push, or fetch still runs, and a success resumes background refresh.

When that stop is active and the cached branch is not behind, Git actions offer Pull (web and desktop menu, and the primary button when the branch otherwise has nothing to do; mobile overview and header do the same).

Why

GitVcsDriver.fetchRemoteForStatus fetches with a 5s timeout. On macOS, Homebrew git uses credential.helper=osxkeychain. After a git upgrade the helper can raise a Security-framework password dialog that those 5s kills before Always Allow can be stored. Failures were backed off forever (30s up to 15 minutes), so the prompt kept returning.

Clearing credential.helper on every background fetch would also drop silent keychain and gh auth git-credential success. The background env is unchanged. Explicit git pull --ff-only still has no non-interactive env and a 30s timeout, so the dialog can be approved.

UI Changes

Git actions show “Upstream status needs attention. Pull to refresh it.” Pull is available in that state even when the cached branch is not behind, which is what resumes the background fetch.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Fixes pingdotgg#13912

  

[macodev00]

Opened upstream.