Bug: snoozed-notification-tabs should not be persisted on user-computer-profile; remove schema field and entity update logic

[JoshuaRowePhantom]

Summary

docs/design/notifications.md currently specifies that snooze state is persisted on the user-computer-profile entity via a snoozed-notification-tabs string-array field. This is wrong: snooze state is ephemeral and does not need to survive a restart.

What needs to change in the design doc

• Remove all references to persisting snooze state on user-computer-profile.
• Remove the snoozed-notification-tabs schema addition from the file checklist.
• Remove the entity-update logic described for snooze (writing to / reading from user-computer-profile).
• Snooze state should be held purely in-memory in NotificationRowViewModel.IsSnoozed (or an equivalent in-process service); it resets on restart.

Affected design sections

• §Snooze (lines ~148–165): remove persistence paragraph.
• File checklist entry: JsonSchemas/user-computer-profile.json — add snoozed-notification-tabs string array field should be deleted.
• NotificationRowViewModel IsSnoozed property remains, but is no longer backed by a persisted store.

Schema fragment to remove

"snoozed-notification-tabs": {
  "type": "array",
  "items": { "type": "string" },
  "description": "Tab IDs whose notifications are silently auto-read (snoozed). Persisted per-tab."
}

This field should never be added to user-computer-profile.json.

[JoshuaRowePhantom]

Verification Failed

The commit 14991c4 correctly removed snoozed-notification-tabs from the JSON schema and updated the NotificationService.cs comment, but docs/design/notifications.md was not updated as required by the issue.

Remaining violations in docs/design/notifications.md

• Line 36 (docstring on IsSnoozed): "Persisted per-tab in the user-computer-profile entity."
• Lines 159-160 (Snooze section): "Snooze state is persisted per tab key in the user-computer-profile entity under a snoozed-notification-tabs string array field."
• Line 259 (file checklist): "JsonSchemas/user-computer-profile.json -- add snoozed-notification-tabs string array field"
• Line 264 (Non-goals Bump actions/checkout from 4 to 7 #1): "snooze state is persisted"

The issue explicitly requires removing all four of these references.