Fix mobile controls hiding immediately when tapped after first play

[MattiasBuelens]

Summary

• After first play, once the controls auto-hide, tapping the mobile player showed the controls on press and hid them again on release.
• Cause: rememberControlsVisibility used remember(firstPlay, paused, forceVisible) { derivedStateOf { ... } }, so it built a new visible State every time one of those inputs changed. toggleControlsOnTap uses pointerInput(Unit), so it keeps whichever State existed at the first pointer event, typically the tap on play, before firstPlay flips. In that stale state "not played yet" means "visible", so it reports true forever, and every tap ends in hideControls().
• Fix: read the inputs through rememberUpdatedState and keep a single derivedStateOf in a plain remember { }, so visible is one State for the life of the composable.
• Hardening: toggleControlsOnTap now wraps its State and callbacks in rememberUpdatedState, so its pointerInput(Unit) handler always uses the latest values even if a caller passes a new State. It's now a @Composable modifier factory, which is fine because it's internal and has one call site.
• The regression came in with 0089217 ("Share UIController core between mobile and TV"). That commit isn't on main or in any release, so no changelog entry.

Test plan

• New ControlsVisibilityTest (6 tests): State stays the same across input changes, plus the ready delay, show/hide-delay, hide(), paused and forceVisible behaviour
• New UIControllerTapTest: tap, play, auto-hide, tap shows the controls and they stay, tap again hides them
• New ToggleControlsOnTapTest (3 tests): the handler uses a swapped-in State and swapped-in callbacks, plus the existing tap-to-show/tap-to-hide behaviour
• The regression, tap and swap tests fail without the fixes and pass with them
• ./gradlew :ui:testDebugUnitTest :ui-common:testDebugUnitTest :ui-tv:testDebugUnitTest
• ./gradlew :ui:lintDebug: no new warnings

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