Avoids the `!debugNeedsPaint` assertion in RenderRepaintBoundary.toImage
when the boundary is still dirty at capture time on slower runners.

Also temporarily narrows macos-integration-tests workflow to
examples/controls/core::test_row.py to validate the fix in CI.

The macOS runner upgrade (macos-14 → -15 → -26) increased the default
viewport size, making the Row alignment screenshots flake with
`!debugNeedsPaint` because the screenshot package's 20ms post-delay was
no longer enough to flush a paint of the larger surface.

Calling resize_page(800, 1000) restores deterministic paint workload.
Reverts the earlier endOfFrame attempt, which deadlocks under the
flutter_test fake scheduler.

To capture more diagnostic output for the test_alignment screenshot
race investigation. Revert before merge.

The OS window resize triggered by resize_page propagates asynchronously.
Without an explicit settle, it races into the capture's post-delay and
re-dirties the RepaintBoundary right before toImage() runs, tripping
`!debugNeedsPaint`.

CI debug log showed the window UPDATE_CONTROL_PROPS arriving 1ms after
the capture invocation was sent.

The resize_page workaround introduced its own race: macOS window resize
is OS-async beyond Flutter's pump cycle, the requested height is clamped
to the runner's display, and the late-arriving resize event re-dirties
the boundary anyway. Revert and rely on the 200ms capture delay only.

Use pump_times to outlast any scrollbar-fade or SafeArea inset
adjustment that might keep the boundary dirty for ~1.5s.

Diagnostic — narrowing down the !debugNeedsPaint cause.

The page is already scrollable; the inner Column.scroll=AUTO produces a
double-scroll layout that combined with intrinsic_width wrapping in the
test harness keeps the RepaintBoundary perpetually dirty, tripping
!debugNeedsPaint when the screenshot is captured.

PR #6450 wrapped the scrollable child in a LayoutBuilder to read viewport
size for the min-height constraint. LayoutBuilder reports 0 for intrinsic
dimensions, which collapses any ancestor IntrinsicWidth / IntrinsicHeight
and leaves the layout in an unstable state — the test harness's
intrinsic_width=True wrapper then perpetually marks the RepaintBoundary
dirty, tripping !debugNeedsPaint when toImage() runs.

MediaQuery.sizeOf exposes the same viewport size through a regular
InheritedWidget, transparent to intrinsic queries, while
SingleChildScrollView already forwards cross-axis intrinsic queries to
its child. Net effect: vertical alignment in scrollable Page/View still
works (the original #6450 intent), and IntrinsicWidth/Height ancestors
are no longer broken.

Restores scroll=AUTO on the alignment example to validate the fix.

…yBoxes

PR #6450 used a LayoutBuilder to read the parent's constraints and apply
the viewport's max-extent as a min-height on the scroll-view child, so
vertical alignment works in scrollable Page/View when content is shorter
than the viewport. LayoutBuilder, however, reports 0 for intrinsic
dimensions, which collapses any ancestor IntrinsicWidth / IntrinsicHeight
and leaves the layout perpetually dirty (test_alignment was tripping
!debugNeedsPaint in toImage()).

Replace the LayoutBuilder with two cooperating RenderProxyBoxes that
forward intrinsic queries to their child:

* _OuterConstraintsReader sits outside Scrollbar/SingleChildScrollView
  and captures its incoming constraints during performLayout.
* _InnerConstraintsEnforcer sits inside SingleChildScrollView and reads
  the captured value back, applying it as a min on the scroll-view child.

Same render output as the original LayoutBuilder (including correct
no-op behavior for nested-in-unbounded-scroll cases), but transparent to
ancestor IntrinsicWidth/Height.

…t change

The inner enforcer lives inside SingleChildScrollView, which provides
unbounded constraints in the scroll axis to its child. On window resize
those constraints don't change, so Flutter's layout pipeline skips the
inner enforcer's performLayout — and it keeps applying the stale min
captured on first layout. Result: vertical alignment looks correct
initially but freezes at the original viewport size after a resize.

Track the inner enforcer in the constraints holder; when the outer
reader sees its incoming constraints change, mark the inner dirty via
invokeLayoutCallback (which enables mutations during layout). The inner
then re-runs performLayout later in the same pass with the updated
holder value.

Revert the temporary narrowing that scoped runs to test_row.py while
diagnosing the !debugNeedsPaint regression introduced by PR #6450.