Preserve Decodex project enabled state on refresh

[yvette-carlisle]

Summary

• preserve the existing project enabled/disabled toggle when runtime paths refresh project config rows
• keep decodex project add as an explicit enable action
• document the refresh versus enable/disable boundary

Verification

• cargo test -p decodex project_config_refresh_preserves_disabled_state
• cargo test -p decodex state_store_open_refreshes_pubfi_project_registry_across_instances
• cargo make checks