Native Windows notifications that stay in Notification Center and jump to the session when clicked #169

This was generated by AI during triage.

Summary

Replace the tray balloon tips with native Windows notifications that stay in Notification Center and, when clicked, jump to the session and bring CSM forward.

Today

ToastHelper shows tray balloon tips. They disappear after a few seconds, aren't kept in Notification Center, and clicking one doesn't take you to the session that raised it. If you were away from the desk, the alert is gone.

Herdr v0.9.4: "Windows notifications stay in Notification Center. Clicking one jumps to its pane and brings the terminal window forward."

Proposal

• Toasts. Use the Windows App SDK AppNotificationManager or Microsoft.Toolkit.Uwp.Notifications. Confirm an OSI licence (OSS-only dependency rule) and that it works from a non-packaged WPF app — an AUMID / Start-menu shortcut may be needed, and the MSI already installs one.
• Content. Title is the session name. Body is the alert ("Approval needed: Bash(npm test)", "Waiting for input", and later "Done" from Show which sessions have an agent actively working, plus an activity timeline across sessions #154). Arguments are session=<id>.
• Activation. Restore and activate the window, call FocusSession(id) (so keyboard focus moves too), and clear the alert.
• De-duplication. Group notifications per session, and replace the previous toast for the same session instead of stacking them.
• Settings. Respect ShowToastNotifications. Remove the session's toasts from Notification Center when its alert clears in-app.

Related: #149 (tray / keep running), #154 ("done" notifications), #5 (notification noise).