Improve plugin conflict recovery and startup experience

[wisdomqin]

What changed

• replace the native startup failure dialog with a localized DSH Desktop recovery surface
• detect and present one or more offending plugins, remove only those plugins, and continue checking after restart
• refresh the startup screen with the pixel whale animation and remove the progress bar
• require a stable Harness health window before leaving the startup screen
• route manual Harness restarts through the active recovery state machine
• guard window navigation so stale startup or recovery loads cannot replace the latest view

Why

A failed plugin could stop Harness before the normal application loaded. Restarting Harness from the recovery screen bypassed the pending recovery action, leaving the app permanently stuck on the startup screen.

Impact

Users get a clear recovery flow that preserves workspaces, sessions, model configuration, and unrelated plugins. If the same conflict remains after a manual restart, DSH Desktop returns to the recovery screen instead of hanging.

Validation

• npm test — 24 files, 135 tests passed
• npm run typecheck
• npm run build
• npm run package:dev:dir
• git diff --check
• packaged macOS development build tested with a real dsh-better-sidebar conflict; manual restart briefly showed the startup screen and returned to recovery without hanging