fix(startup): handle when the user has not decided the storage type (App-Private/Public)

[david-allison]

Assisted-by: Claude Fable 5
implemented after a long discussion: comments, discussion and naming are mine

Purpose / Description

This is theoretical and works in order to get ExternalEntryPointsUndecidedStorageTest working.

I want to move AnkiDroid away from implicit collection creation in withCol into a deferred 'startup' path in order to remove complexity, allow for easy migration of CollectionHelper/CollectionManager to :anki-common, and better support for choosing a non-public AnkiDroid folder:

• Don't force full (F-Droid/GitHub) releases users to grant the All files access permission #13574

Fixes

• Fixes some of Consolidate validation in app entry points #19552
• Yak shave for Architecture Discussion: Module Extraction #20737

Approach

If the storage location is undecided:

• Redirect to IntentHandler if in the app
• ⚠️ Crash the content-provider API, as this cannot be handled from the user's perspective
  • Optional follow-up: we may want to add a follow-up issue to handle this more gracefully on
  • Optional follow-up: do we want to add a localized exception message?

How Has This Been Tested?

This code exists to make a unit test pass

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner