Feature: Git remote helper integration

[aloth]

Add a git-remote-helper so users can interact with Overleaf projects using native git commands:

git clone overleaf::https://www.overleaf.com/project/<id>
git pull   # fetch latest from Overleaf
git push   # push local commits to Overleaf

This would be an additive feature - all existing olcli commands continue to work as before. The git-remote-helper provides an alternative interface for users who prefer native git workflows, real commit history, and offline batching.

Originally proposed in #15 by @bicheTortue. The core concept is solid but the original PR was based on v0.1.7 and the codebase has evolved significantly since. A fresh implementation can leverage the current OverleafClient and sync infrastructure directly.

Planned for a future release before v1.0.0.

[aloth]

Shipped in v0.7.0. The git-remote-overleaf helper is now available via npm i -g @aloth/olcli.