Fix git auth fallback for non-interactive environments

[patmakesapps]

Problem

The _run_git_interactive fallback for auth requires an interactive terminal. In non-interactive contexts (headless Raspberry Pi, systemd service, Docker), this can hang indefinitely.

Proposed solution

• Detect whether the environment is interactive before attempting interactive git auth.
• Provide a non-interactive fallback with a clear error message.
• Support token-based auth as an alternative.

Implementation notes

• Check sys.stdin.isatty() before calling _run_git_interactive.
• Support GIT_TOKEN or GITHUB_TOKEN env vars for non-interactive auth.
• Add a configurable timeout to prevent indefinite hangs.

Acceptance criteria

• Git operations in non-interactive environments fail gracefully instead of hanging.
• Clear error message explains how to configure auth for headless use.
• Token-based auth works when the env var is set.
• Interactive auth still works when a TTY is available.