US-13 — Open a notification

## User story

As a notification author, I want to open a notification from the list so that I can review its content and delivery details.

## Acceptance scenarios

```gherkin
Feature: Open a notification

Background:
Given the author is viewing all notifications

Scenario: Open a notification from its subject
When the author selects a notification subject or title
Then the selected notification should be opened

Scenario: Open a draft notification
Given the notification has status "draft"
When the author opens the notification
Then its existing content should be displayed
And it should be available for editing

Scenario: Open a scheduled notification
Given the notification has status "scheduled"
When the author opens the notification
Then its existing content should be displayed
And its scheduled delivery details should be displayed

Scenario: Open a dispatched notification
Given the notification has status "dispatched"
When the author opens the notification
Then its content and delivery details should be displayed as read-only
```

Start by locating the all-notifications list and the flow used when selecting a notification subject or title. Verify each status scenario: drafts retain editable content, scheduled notifications show delivery details, and dispatched notifications show content and delivery details as read-only.

Written by the indexing model from the issue text.