GeezerVison

…der external auth

Adds CreateWorkspacePage.stories.tsx with four stories covering the
multi-provider external auth bug described in #22420:

- MultipleExternalAuth: both buttons render enabled
- ClickingOneAuthDoesNotDisableOthers: regression test for #22420
- OneProviderAuthenticated: mixed authenticated/unauthenticated state
- SequentialAuthFlow: full polling flow with mockResolvedValueOnce

The external auth polling state was a single shared value for all
providers. Clicking one provider's Login button set the global state to
"polling", which disabled every other provider's button. Users had to
refresh the page between each authentication.

Change the state from a single ExternalAuthPollingState string to a
Record<string, ExternalAuthPollingState> keyed by provider ID. Each
provider now independently tracks idle, polling, and abandoned states.
The query refetchInterval activates when any provider is polling and
each provider has its own 60-second timeout.

Fixes #22420

… MockTemplateVersionExternalAuthAzure

…ed external auth

…oviders