Port the Write-Ahead Log implementation from raft/ into the VSR
server. Log entries are now written to disk with FNV-1a checksums
and fsynced before updating in-memory state. On startup, the WAL
file is loaded and validated, replacing the boot marker for crash
detection. View changes and recovery use atomic rename (tmp.log ->
vsr.log) to replace the WAL safely.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
cozisandClaude Opus 4.6