onboarding_check

Post-install onboarding is checked on every activation, not via a dedicated install event.
installation_event_trigger is satisfied because `activate` always calls open-thanks-for-installing.ts.
The check reads global state key `onboarding` via onboarding-state.ts:
- `onboardingMessageShown` — when false, open the onboarding webview panel via onboarding-panel.ts.
- `lastVersion` — updated each activation after the message has been shown so future releases can detect extension updates.
The call is fire-and-forget; errors are logged and do not fail activation.

Interactive page: onboarding_check