Compute resize and damage from the previous published scene

evidence/native-scene-transition-owner-20261005/SCOPE.md

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+# Use the original scene and size owners for frame transitions
+
+Base: merged native70 c5e7eba344bd2982f30338e8acd18210e19de2ac.
+Same completed native checkout; Text70/68/69 source proofs and wheels retained.
+
+Source finding: reflow_visible substitutes an empty predecessor when the last
+committed scene is a full map. Its damage comparison then treats the root and
+unchanged chrome as new. Full reflow after scrolling also uses the old full map
+for damage instead of the latest viewport scene. These are source-supported
+wrong predecessor choices, not attribution of the original RichVisual sample
+or a measured CPU/FPS improvement.
+
+Compositor owns the existing published scene map. Make that acquisition carry
+reflow, visible reflow, lazy full geometry publication and layer projection;
+delete their independent predecessor choices. Keep logical show/hide membership
+and conservative viewport exposure separate: a complete geometry query does
+not prove that every widget has consumed native size publication. Capture
+geometry and current-placement validity retain their existing contracts.
+
+Widget._size_updated already owns size, virtual extent and container changes
+and explicitly returns whether a Resize event should be sent. Screen must use
+that result instead of the parallel region-size-only ReflowResult.resized set.
+Delete the set, field, comparison and every consumer. ScrollView keeps its
+independently authored virtual extent and container projection but reuses the
+existing Widget size commit; its original scrollbar resource retirement stays
+with its existing scrollbar update behavior. No change to the size-hook ABI or
+Toad Body/Window callbacks.
+
+AST and complete declaration/caller/lifetime reading precede edits. Preserve
+native show/hide order, viewport geometry targets, stable paint ties, authored
+scroll extents, scrollbar feedback, capture and lazy-layout semantics. No new
+map/cache/type/state flag, caller-built readiness predicate or alternate paint
+path. Native Compositor/Screen/ScrollView only; no Toad writes.
+
+Batch source and affected native App checks after the coherent implementation.
+Existing Heisenberg workflow owns the next meaningful changed installed frame
+and motion qualification; no repeat of native70/68/69 controls, provider,
+recording, environment, installed package or native SDK build. Source-only
+until those boundaries are qualified. CI is deferred; results are recorded
+without adding a delivery wait.