Resume from Interruption

Why: Long bisections (especially git source builds) can take hours/days. If interrupted, all progress is lost.

Details:
- Save bisection state periodically (current commit, test results, bisect log)
- Detect incomplete bisection on startup and offer to resume
- Store state in /var/local/kernel-auto-bisect/bisect_state.json
- Check if git bisect is in progress and restore GOOD_REF/BAD_REF