US-06 — Select communication channels

## User story

As a notification author, I want to select the communication channels through which the notification will be delivered so that it is routed to the appropriate App and Email campaigns.

## Acceptance scenarios

```gherkin
Feature: Select communication channels for immediate send

Background:
Given the author is composing a notification
And they want to send it immediately
And the communication-channel options are displayed in the "Delivery & timing" section

Scenario: Select App Notification
When the author selects "App Notification"
Then "App Notification" should be shown as selected
And the notification should be routed to the App Notification channel

Scenario: Select Email Newsletter
When the author selects "Email Newsletter"
Then "Email Newsletter" should be shown as selected
And the notification should be routed to the Email Newsletter channel

Scenario: Select both communication channels
When the author selects "App Notification"
And the author selects "Email Newsletter"
Then both channels should be shown as selected
And the notification should be routed to both channels

Scenario: Deselect a communication channel
Given both communication channels are selected
When the author deselects "Email Newsletter"
Then "App Notification" should remain selected
And "Email Newsletter" should not be selected

Scenario: Attempt to dispatch without a communication channel
Given neither communication channel is selected
When the author attempts to dispatch the notification
Then the notification should not be dispatched
And a validation message should explain that at least one channel is required

Scenario: Store the selected communication channels
Given the author has selected one or more communication channels
When the notification is saved
Then the selected communication channels should be stored against the notification

... Out Of Scope for Immediate Send ...

Scenario: Attempt to schedule without a communication channel
Given neither communication channel is selected
And the author has selected "Scheduled"
When the author attempts to schedule the notification
Then the notification should not be scheduled
And a validation message should explain that at least one channel is required

```

Start by locating the notification-composition flow and the "Delivery & timing" section in the TypeScript project, then trace how dispatch and notification saving currently work. Use the acceptance scenarios as the completion checklist: both channels can be selected or deselected, at least one is required for dispatch, and selected channels are stored and routed correctly.

Written by the indexing model from the issue text.