Implements gt-b2hj: Uses git fsck --unreachable to find orphaned commits
that were never merged to main.
Features:
- Filters to commits only (not blobs/trees)
- Date filtering (--days=N, default 7)
- Excludes stash commits (WIP on, index on, etc.)
- Excludes routine bd sync commits
- Shows recovery hints (cherry-pick, show, branch)
07a40771da