When user hits "back" to the rep-selection page, resurface their original query (same session only)

[oddball-lindsay]

Background

What happens when a user hits "Back" on contact-representative?

The team discussed and decided...

If the user hits "Back" in the same session:

1. The selected representative is null-ed out
2. The user can see the query they just entered
   1. We'll cache the user's rep query on the frontend to support this
3. The user will need to select a rep (same or a new one) to move back to contact-representative
   1. If the user tries to "Continue" we will throw the validation error

---

If an authenticated user leaves the form experience and revisits the representative-selection page later via the "Back" button, they will see the default flow:

1. The selected representative is nullified
2. The user will need to reenter their query (we will be unable to preserve because this is a new session)
3. The user will need to select a rep (same or a new one) to move back to contact-representative
   1. If the user tries to "Continue" we will throw the validation error

Tasks

• [ ] Implement frontend logic to preserve a user's representative query in the same session
• [ ] Implement frontend logic to nullify the rep selection, if the user hits "back" to revisit the representative-selection screen

Acceptance Criteria

• [ ] When user hits "back" to the rep-selection page, they are able to see the representative query they just entered and can re-select a representative from the search results.

[cosu419]

This is ready for review @mtri

[mtri]

QA ticket: https://github.com/department-of-veterans-affairs/va.gov-team/issues/93957