Flip the order: do a targeted GET filtered by repo name first, and
only POST if the repo doesn't exist yet. This avoids expected 400s
showing up in devtools and Sentry when the background link_all_repos
task has already created the repo.

Replace direct Client.requestPromise usage with fetchMutation which
wraps the same call but is the recommended API.

fetchMutation only accepts PUT/POST/DELETE methods. Use the shared
QUERY_API_CLIENT instance directly for the imperative GET call.

Replace deprecated QUERY_API_CLIENT.requestPromise with the sanctioned
queryClient.fetchQuery + fetchDataQuery pattern for imperative GET
requests outside of React Query hooks.

Use ApiQueryKey type with getApiUrl for proper URL typing, satisfying
the queryKey constraint on queryClient.fetchQuery.

With link_all_repos running in the background after integration
install, all repos are automatically registered in Sentry. The
hide-on-deselect and cleanup-on-switch logic was designed for manual
repo registration and is now counterproductive — it removes repo
records that the background task created, causing them to disappear
from settings. Selection is now just a context pointer.

Rewrite tests to match the GET-first-then-POST approach and removal
of repo hide/cleanup logic. Remove tests for cleanup-on-switch and
hide-on-remove since those behaviors no longer exist.

Match on r.name === repo.identifier instead of externalSlug because
externalSlug varies by provider (GitLab uses a numeric project ID,
VSTS uses external_id). Repository.name is consistently the full
repo path across all providers.

…rage

Remove unnecessary async from handleRemove test to fix require-await
lint error. Rename misleading test name to accurately reflect that only
POST fails (GET succeeds with empty results). Add dedicated test for GET
failure scenario. Simplify busy state test by removing waitFor dance
that couldn't observe the intermediate state.