Support GitHub App authentication for Squad-authored commits #256
Description
Summary
Allow Squad to authenticate as a GitHub App so that AI-authored commits, PRs, and actions show up under an app identity rather than a user account.
Origin: Discussion #179 by @msquibb
Why
- Clearer audit trail for AI vs human contributions
- Better compliance for organizations tracking AI-authored changes
- Aligns with GitHub's app-based authentication patterns
Scope
- Configure Squad to use GitHub App credentials for git operations
- PR authorship shows app identity instead of user identity
- Maintain backward compatibility with personal token auth
Notes
This requires GitHub App infrastructure setup. Investigate feasibility of using installation tokens for git push and gh CLI operations.