Stop counting locked phones, keyboards and home screens as screen time

[jsconu]

Fixes three bugs reported from real use of the parent app. A fourth, the crash on removing a blocked website, still needs a stack trace; it's not in this PR.

Fourteen hours in a day, and an undercounted browser

Three separate causes, all in how time gets attributed:

Cause	Effect	Fix
The 30-second tick kept crediting the app in front while the phone was locked	Whatever was open when the phone was put down accrued time all night	The accessibility service now hears screen off and unlock itself, and credits nobody while the screen is off
An open session counted until its screen-off was heard, and rollover never cleared the session's start	A missed screen-off counted every locked hour, and a new day could start with the previous evening already on the clock	A session only counts while the screen is on; one still open at midnight counts on the new day from midnight
Keyboards, the notification shade and the home screen were credited as apps	Typing a search took the credit away from the browser until the keyboard closed	Overlays leave the credit with the app underneath; the home screen is screen time but nobody's app time

The report guessed the 14 hours came from system apps. The evidence points at the first two rows instead — though the third row is real too, just as the reason the browser looked undercounted.

Leaving the calm notification list took several Back presses

Every route to it (the dashboard card, the calm notification, the Quick Settings tile) pushed another copy of the screen, and the open_digest intent extra survived activity recreation, so a theme change or the app lock pushed yet another. The extra is now consumed once, and the screen is never stacked on itself (launchSingleTop). The kid app uses a state switch rather than a navigation stack, so it never had this.

Tests

OvercountTest adds nine cases, each of which fails against the old code: a missed screen-off, a session across midnight, a new day starting with yesterday's evening on it, an unlock after a missed screen-off, and the window classification. All 290 shared unit tests pass; every variant builds.

Not verifiable without a phone: the screen-off receiver and rootInActiveWindow on unlock. Test APKs are built for a device check before merge.

🤖 Generated with Claude Code