fix: stop the permission-required screen flashing at launch when access is granted

[brendan-ch]

Problem

When launching the app with Screen Time access already granted, the ScreenTimeAccessRequiredView flashes briefly before landing on MainView.

Root cause

FamilyControls loads authorization asynchronously and reports a stale .notDetermined for the first moments after a cold launch — even for a user who granted access (Apple Developer Forums 747915). RootView captured that stale value once at init (ScreenTimeAuthorization.init) and only corrected it when the scene became active, so RootDestination.resolve mapped the transient non-.approved status to .screenTimeAccessRequired for a frame or two before flipping to .main — the visible flicker.

Onboarding only completes on .approved, so a post-onboarding .notDetermined at launch is almost always this stale value settling to .approved.

Fix

Treat .notDetermined as .main. Only .denied routes to .screenTimeAccessRequired:

• RootDestination.resolve returns .main for every post-onboarding status except .denied. The overwhelmingly common launch (access already granted, momentarily reported as a stale .notDetermined) shows the real app immediately, with no flash of the access-required screen. A genuinely revoked user may see .main briefly at launch before the status settles to .denied and flips them to the access-required screen — a rare case where a momentary flicker is acceptable.
• ScreenTimeAuthorization.resolveAtLaunch() stays: it re-reads while the status is .notDetermined (bounded ~500ms) so a revoked user's .denied surfaces promptly rather than waiting for the next foreground.
• Removes the now-unneeded resolving machinery: the .resolvingAuthorization case, LaunchResolvingView, and ScreenTimeAuthorization.hasResolvedStatus.

Test plan

• RootDestinationTests — non-.denied post-onboarding statuses (.approved, .notDetermined) route to .main; .denied routes to the access-required screen; onboarding-incomplete always routes to onboarding.
• ScreenTimeAuthorizationTests — resolveAtLaunch settles past a stale launch-time .notDetermined to a revoked user's real .denied; gives up gracefully when the status never settles.
• Full unit-test target green: 353 tests in 61 suites passed.
• On-device manual check (FamilyControls async behavior doesn't reproduce on Simulator): cold-launch with access granted → main flow immediately, no access-required flash; with access revoked → main flow briefly, then access-required.

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