Tighten TestReconnect_GapBeyondRetainedWal_NeedsRebuild assertion from
"NeedsRebuild or Degraded" to strictly "NeedsRebuild". The handshake
R < S path returns NeedsRebuild directly — tolerating Degraded weakened
the proof.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>