feat(properties): harden standalone properties lifecycle

- synchronize child appearance and hidden-window readiness
- serialize native Torrent mutations transactionally without double-encoded rows
- preserve native lifecycle markers and fence stale or duplicate actions
- remove the obsolete modal surface and ignore implementation_plan.md

.gitignore

@@ -64,6 +64,7 @@ build/
 # Local secrets and signing material
 .env
 .env.*
+implementation_plan.md
 *.key
 *.pem
 !src-tauri/binaries/_internal/certifi/cacert.pem