PluginManager::broadcast_notification was fanning out host notifications to every loaded plugin. Only V4 plugin processes can receive host->plugin notifications; V2/V3 plugins correctly rejected them with notify_plugin requires V4 protocol.
Add PluginProcess::is_v4() and skip non-V4 plugins in broadcast_notification so V4 document snapshot notifications only go to V4-capable plugins. Fixes repeated console errors for Example, Land Survey and V2 Compat.
- Run Plugin Manager release fetches on OS threads so they execute in
parallel instead of serialising on the async executor.
- Reduce V4Connection shutdown poll from 3s to 100ms; the runner is killed
and reaped without blocking host shutdown.
- Add PluginManager::remove and PluginProcess::shutdown_and_wait so
uninstall can stop the runner before deleting files, fixing Windows
access-denied errors on plugin removal.
- Rebuild ribbon immediately after uninstall so the tab disappears.
Sebastian