test(settings): fold local-enable tests into shared files, drop issue-numbered names

Nina's review on #1713: standalone issue-numbered test files proliferate one-offs where shared setup already exists. Move TestIsSetUpAndEnabled_LocalSettingsOnly into settings_test.go (reusing its existing testutil.InitRepo pattern) and the e2e hook-flow reproduction into integration_test/setup_cmd_test.go, which already owns the enable/disable/hooks-gating test suite. Also strip the remaining "#1123" breadcrumb from the settings.go doc comment. All assertions are unchanged; only file placement and naming moved.