Restore new combobox + fixes

[edisile]

Done

Reapplied reverted combo box PR (#5617) along with a few fixes. The reverted code has already been reviewed, so you can skip it and review only the new changes by comparing the tip of this branch to the reapply commit: b25b1b5

The reverted version had a problem where navigating to a nested brand store route and refreshing the page would bring you back to /admin/< store id >/snaps rather than the page you were viewing before. Fixes:

• compare current store id with selected store id in StoreSelector component, call navigate(...) only if they're different
• improved ComboBox behavior during init (onChange doesn't fire until there are some options to choose from)

As a drive-by I added a primary navigation fix for highlighting the "Models" section when visiting remodel pages

How to QA

• visit https://snapcraft-io-5670.demos.haus/admin/ahnuP3quahti9vis8aiw/models/test-superalpaca-00/remodel
  • the "Models" link in the side nav should be highlighted
• refresh the page
  • the URL doesn't change
• select a different store
  • the URL changes to /< store id >/snaps

Testing

• This PR has tests (restores previously merged tests)
• No testing required (explain why):

Security

• Security considerations for review (list them):
  • Examples:
  • Access control: users can only access their own data
  • Input: user input is validated and sanitised
  • Sensitive data: secret or private data is not exposed in any way
  • ...
• This PR has no security considerations (explain why):

Issue / Card

Fixes #

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[webteam-app]

Demo

Jenkins

demos.haus

[Copilot]

Pull request overview

Reapplies the accessible Downshift-based ComboBox and refactors the publisher-side store switcher to use it, addressing a refresh/navigate regression for nested brand store routes and improving nav highlighting for remodel-related model pages.

Changes:

• Introduces a new ComboBox component (Downshift) with accompanying SCSS and unit tests.
• Refactors StoreSelector to use ComboBox and avoids navigating on mount when the selected store matches the URL store id.
• Adjusts PrimaryNav “Models” highlighting to remain active on nested model/remodel routes.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
static/sass/styles.scss	Imports and includes the new combobox SCSS mixin in the main stylesheet pipeline.
static/sass/_snapcraft_p-combobox.scss	Adds new .p-combobox styling used by the Downshift-based component.
static/sass/_snapcraft_l-application.scss	Removes the old .store-selector styling that is no longer used after the refactor.
static/js/publisher/components/StoreSelector/StoreSelector.tsx	Replaces custom store selector UI with the new ComboBox and guards navigation on mount.
static/js/publisher/components/StoreSelector/tests/StoreSelector.test.tsx	Adds tests to ensure StoreSelector renders correctly and only navigates on actual changes.
static/js/publisher/components/PrimaryNav/PrimaryNav.tsx	Updates “Models” nav selection logic to cover nested remodel/model routes.
static/js/publisher/components/ComboBox/ComboBox.tsx	Adds the new ComboBox component and state/behavior patches around Downshift.
static/js/publisher/components/ComboBox/tests/ComboBox.test.tsx	Adds unit tests for ComboBox interactions, filtering, and keyboard behavior.

[ilayda-cp]

changing to "includes" makes it too loose. It might work now but in the future if we add something like "/admin/${storeId}/models-archive" it would cause a bug.