fix broken .git on push

[tikinang]

Description

Fix broken .git after push - write the temporary git objects to a quarantine dir in tmp instead of the repo, and drop the git prune that deleted staged blobs.

How to reproduce the bug

# 1. A fresh repo with one commit and a valid zerops.yml for your service
mkdir /tmp/zcli-prune-bug && cd /tmp/zcli-prune-bug
git init -q -b main
cat > zerops.yml <<'EOF'
zerops:
  - setup: app
    build:
      base: ubuntu@latest
      deployFiles: ./
    run:
      base: ubuntu@latest
      start: sleep infinity
EOF
git add -A && git commit -qm init

# 2. Stage a new file but do NOT commit it
echo hello > staged.txt
git add staged.txt
BLOB=$(git rev-parse :staged.txt)
git cat-file -t "$BLOB"        # prints: blob

# 3. Push with the default workspace state (all)
zcli push --project-id <PROJECT_ID> --service-id <SERVICE_ID> --setup app --no-wait --disable-logs

# 4. The staged blob is gone and the repo is broken
git cat-file -t "$BLOB"        # fatal: git cat-file: could not get object info
git fsck                       # missing blob <BLOB>
git commit -m "commit staged"  # error: invalid object 100644 <BLOB> for 'staged.txt'
                               # error: Error building trees