Find Regression Commit

Define a deterministic good/bad oracle and known boundary commits. Read bisect workflow.

Honor existing local feedback, but do not install hooks or change historical candidates during bisection.

Run bisect in an isolated worktree. Distinguish unavailable prerequisites from the target regression; a compiler failure can itself be the requested bad behavior. Save the bisect log, reproduce the reported candidate and relevant predecessor, reset the bisect, and report ambiguity caused by skips.