US-25 — Edit the headline for app alert type

## User story

As an app alert notification author, I want to enter a concise headline so that recipients receive a clear breaking-news headline.

## Acceptance scenarios

```gherkin
Feature: Edit an app alert notification headline

Background:
Given the author is composing an app alert

Scenario: Import a valid headline
When the author imports an article
Then the headline of the article should appear in the headline field
And the character counter should display the character count

Scenario: Have a headline at the maximum length
When the author enters a headline containing fewer than [max count] characters
Then the headline should be accepted
And the character counter should display count/90

Scenario: Attempt to exceed the headline limit
When the author enters a headline containing more than [max count] characters
Then the headline should offer a non-binding warning that the limit has been exceeded
And the author should be informed of the character limit

Scenario: Attempt to dispatch without a headline
If the headline is empty
When the author attempts to dispatch the app alert notification
Then the notification should not be submitted
And a validation message should be displayed against the headline
```

No file, test, or entry point is named in the issue. Start by locating the app alert composition view and its headline field, then identify the existing validation and character-count tests, if present. Done means imported headlines populate the field, the counter uses 90 as the reference, overlong text gives a non-blocking warning, and an empty headline prevents dispatch with validation feedback.

Written by the indexing model from the issue text.