* volume.configure: keep the superblock in sync with the .vif
ConfigureVolume only rewrote the .vif's replication field, leaving the
.dat superblock stale. A mounted volume also kept reporting the old
placement in heartbeats, and its next compaction would rewrite the stale
placement into a fresh .dat.
Parse the placement once, then update the live volume when mounted: the
in-memory .vif copy and superblock, and the .dat header through the
volume's own backend under the data-file locks. For unmounted volumes
rewrite the header directly; remote-only volumes skip it since the .vif
carries the placement.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* volume.configure: update the .dat superblock in the Rust volume server
Mirror the Go ConfigureVolume change: after rewriting the .vif, rewrite
the replica placement in the .dat header too, so a remounted volume's
superblock, heartbeats, and later compactions agree with the .vif. A
missing .dat (remote-only volume) is skipped since the .vif carries the
placement.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
---------
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
