Add notification concept and reference docs

[nscuro]

No description provided.

[Copilot]

Pull request overview

Adds first-class documentation for the notifications concept and a reference for notification groups, and wires both into the docs navigation/cross-links.

Changes:

• Introduces a new “About notifications” concepts page describing alerts, publishers, templates, levels, scopes, groups, and triggers.
• Adds a new reference page enumerating notification groups (with scope/trigger/level) and links to it from filter expression docs and reference nav.
• Updates concepts navigation labels (“About …”) and fixes an incorrect “alerts” link in the notifications design doc.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
docs/reference/notifications/groups.md	New reference page listing notification groups and their metadata.
docs/reference/notifications/filter-expressions.md	Adds cross-link to notification groups.
docs/reference/notifications/.pages	Adds “Groups” entry to notifications reference nav.
docs/concepts/vulnerability-policies.md	Renames H1 to “About vulnerability policies”.
docs/concepts/notifications.md	New concepts page explaining the notification framework.
docs/concepts/architecture/design/notifications.md	Fixes “alerts” link to point to the concepts page.
docs/concepts/access-control.md	Renames H1 to “About access control”.
docs/concepts/.pages	Updates nav labels and adds “About notifications”.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.