Export guest state through the shared folder

[btsouth]

Add an in-guest export path that archives home and configuration into the mounted 9p share. The goal is to let trial users carry their setup into a full installation.

[btsouth]

Configuration export and restore are available in v0.0.11-preview; #26 is consolidated here. The remaining check is a real restore onto a fresh Omarchy install, confirming settings, theme, and added packages transfer without carrying over VM-specific configuration. This is configuration migration, not a full VM backup.