Stagewise stagewise@1.19.0 Release Notes

validate API spec compliance in endpoint probe and fix UI flicker (3224e1a)
add endpoint reachability test, strict model validation, and context window warning (31b6cba)
refine onboarding UI and fix custom model creation (e2b2bb5)
refactor onboarding into branching flow with model-access selection (64dd216)

revert auth callback scheme to stagewise-dev (4ee064e)
fix stale telemetry in custom endpoint cancel handler (d17a173)
restore missing imports and fix formatting in settings refactor (7b407dc)
adapt sound selection to new notificationSoundPacks UI state after rebase (c0495ba)
resolve 6 onboarding review issues across login, endpoints, models, theme, and form (b8f6831)
address review issues in onboarding flow (0615d97)
use trackAuthCompleted for telemetry on Continue button (29ec5fa)
add signInEmail prop to onboarding login after rebase (c8a9372)
replace fetch with node:http/https for endpoint reachability test (555fe52)
reduce endpoint reachability timeout to 3s and add client-side safety timeout (6923691)
broaden hosted API origin check for dev auth scheme (8647223)
stack model-access options vertically in onboarding (3e70887)
make custom endpoints/models scrollable in onboarding (873d37d)