Do not re-home on an ancestry match that ties between sessions

The Codex app-server daemon hosts every Codex session in one process, so all of them record the same owner and ancestry ties at equal depth; the match then falls to a recency tie-break and can name another worktree's session (#2612). Such a match still links as before, but is no longer treated as an identified agent: it neither re-homes a session into the committing worktree nor skips the other-worktree fallback. The tie-break itself is left to the #2612 fix.