CHI-3736: Mask identifiers in browser notifications

[Copilot]

Description

Replaces the standard new message notification title with a localized masked variant when VIEW_IDENTIFIERS is denied, and removes the IncomingTask notification entirely (modifying it doesn't work). Fixes broken unit tests caused by the missing Notifications mock and adds coverage for the notification deletion.

Test fixes (maskIdentifiers/index.test.ts):

• @twilio/flex-ui mock now includes Notifications.registeredNotifications (Map created inline in factory to avoid Jest hoisting issues with const)
• IncomingTask added to mocked NotificationIds
• mockRegisteredNotifications accessed via the imported module reference post-mock

New test coverage:

• IncomingTask is deleted from registeredNotifications when VIEW_IDENTIFIERS is denied
• IncomingTask is NOT deleted when VIEW_IDENTIFIERS is granted

Checklist

• Corresponding issue has been opened
• New tests added
• Feature flags added
• Strings are localized
• Tested for chat contacts
• [n/a] Tested for call contacts

Other Related Issues

None

Verification steps

Run npm test in plugin-hrm-form — all maskIdentifiers tests pass.

AFTER YOU MERGE

1. Cut a release tag using the Github workflow. Wait for it to complete and notify in the #aselo-deploys Slack channel.
2. Comment on the ticket with the release tag version AND any additional instructions required to configure an environment to test the changes.
3. Only then move the ticket into the QA column in JIRA

You are responsible for ensuring the above steps are completed. If you move a ticket into QA without advising what version to test, the QA team will assume the latest tag has the changes. If it does not, the following confusion is on you! :-P

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