PyTorch Git Bisect for TorchTitan

Bisect the PyTorch repo to find the commit that broke TorchTitan. Always use absolute paths — shell state does not persist between Bash calls.

Phase 1: Gather Information

Record the TorchTitan directory (pwd). Then check if ~/.claude/torchtitan_torch_bisect_cache.json exists — if so, show cached values and let the user reuse or override them.

Collect via AskUserQuestion (pre-fill from cache if available):

1. PyTorch repo path — absolute path to local checkout
2. Build command — shell command to recompile PyTorch after each checkout
3. Test command — run from TorchTitan dir; must exit 0 on good commits, non-zero on bad. Judge ONLY by exit code, never by log content.
4. Good commit — a commit hash or a date (e.g., Feb 15)
5. Timeout policy — if test exceeds 10 min, auto-mark bad or ask each time?