Back left the Manage Libraries sheet open on Android with no way to
dismiss it. The host answered the platform pop with
`BackKeyCoordinator.consumeIfHandled()`, which dedups the focused key
path against the platform pop. Only TV routes one Back through both;
touch platforms never deliver Back to the sheet's key handler, verified
on device — a physical Back produced only `popRoute` and no key event.
So there was nothing to dedup against, and the global one-shot marker,
once set by any other handler, silently swallowed the only signal that
closes the sheet.
Scopes the dedup to TV. The TV regression that guarded this never set
the TV override, so it asserted the swallow on every platform and hid
the defect; it now enables the override and a touch counterpart pins the
dismissal.
Also blocks semantics behind the barrier. The barrier takes every
pointer event but left the screen underneath in the semantics tree, so
assistive tech and UI automation still saw rows that could not be
activated — Maestro read an occluded settings row as visible and tapped
its stale coordinates into the sheet. Flutter's own ModalBarrier blocks
semantics for the same reason.
Verified by replaying the failing Maestro sequence
(.maestro/subflows/settings_deep_checks.yaml lines 42-60) on a device:
back dismisses the sheet, Services opens, and back returns to settings.
The search screens, the out-of-band auth dialogs, the live TV guide and the
list-download paths each carried their own copy of the same shell. Extracts
SearchInputField and PendingAuthDialog and routes the duplicated download
and guide helpers through one implementation.
Extract the manage/reorder-libraries sheet from the libraries screen into
a shared widget with a public launcher, and add a settings tile (top
group, gated on having libraries) that opens it. The libraries screen
keeps its side-nav refresh and re-select-on-hide behavior via launcher
hooks; the TV dialog path lives in the launcher so the entry works there
too.
Desktop overlay sheets defaulted to a fixed 400px max height, which left
the reorder sheet ~280px tall. Both default-constraint sites now use 75%
of window height, matching mobile.
close#1468
Adds nullable canPop + onSystemBack to OverlaySheetHost. When canPop is
set, the host installs its own PopScope that closes an open sheet on a
system/route back instead of popping the screen; null keeps today's
behavior. Lets screens drop their hand-rolled sheet-back PopScopes.
edde746