Fix #32538: Restore spacer page-end effect and optimize relayout scope

Fixes two regressions from spacer relayout changes:
down/fixed spacers on the last system of a page had no effect when
vertical spread was disabled, and system brackets could draw stale
after systems moved between pages during partial relayout.
The spacer trigger is now cost-aware: most edits stay measure-local;
only boundary cases escalate to a bounded range from current system
start to the next system boundary (or score end if none), avoiding
full score relayout on large scores.
Page-end clearance now respects last-system down spacer distance when
vertical spread is disabled.
Also refresh bracket and instrument-name vertical geometry in
restoreLayout2() for reused systems that move across pages.

Author: pedroataidefonseca

src/engraving/dom/spacer.cpp

@@ -27,6 +27,7 @@
 
 #include "measure.h"
 #include "score.h"
+#include "system.h"
 
 using namespace mu;
 using namespace muse::draw;
@@ -177,7 +178,44 @@ void Spacer::triggerLayout() const
         return;
     }
 
-    m->triggerLayout();
+    Score* s = score();
+    System* system = m->system();
+    if (!s || !system || s->nstaves() == 0) {
+        m->triggerLayout();
+        return;
+    }
+
+    // Most spacer edits can stay local to the measure and are much cheaper.
+    // Escalate only for down/fixed spacers on the last non-vbox system of the page,
+    // where edits can repaginate and affect page-end spacing.
+    if (spacerType() == SpacerType::UP) {
+        m->triggerLayout();
+        return;
+    }
+
+    System* nextSystem = m->nextNonVBoxSystem();
+    if (nextSystem && nextSystem->page() == system->page()) {
+        m->triggerLayout();
+        return;
+    }
+
+    // For the last notation system on a page, include the next system boundary
+    // so page-end spacing can be recomputed without relaying out the whole score.
+    Measure* firstMeasure = system->firstMeasure();
+    if (!firstMeasure) {
+        m->triggerLayout();
+        return;
+    }
+
+    Fraction startTick = firstMeasure->tick();
+    Fraction endTick = s->endTick();
+    if (nextSystem) {
+        if (Measure* nextFirstMeasure = nextSystem->firstMeasure()) {
+            endTick = nextFirstMeasure->tick();
+        }
+    }
+
+    s->setLayout(startTick, endTick, 0, s->nstaves() - 1, this);
 }
 
 //---------------------------------------------------------

src/engraving/rendering/score/pagelayout.cpp

@@ -263,9 +263,10 @@ void PageLayout::collectPage(LayoutContext& ctx)
             isPageBreak = (y + dist) >= endY && breakPages;
         }
         if (isPageBreak) {
-            // Reserve only natural bottom clearance against footer on page end.
-            // Spacer down is applied between systems (SystemLayout::minDistance).
             double dist = ctx.state().prevSystem()->minBottom();
+            if (!ctx.conf().isVerticalSpreadEnabled()) {
+                dist = std::max(dist, ctx.state().prevSystem()->spacerDistance(false));
+            }
             double footerPadding = 0.0;
             // ensure it doesn't collide with footer
             if (footerExtension > 0) {

src/engraving/rendering/score/systemlayout.cpp

@@ -2385,6 +2385,11 @@ void SystemLayout::restoreLayout2(System* system, LayoutContext& ctx)
 
     system->setHeight(system->systemHeight());
     SystemLayout::setMeasureHeight(system, system->systemHeight(), ctx);
+
+    // Reused systems can move across pages during partial relayout.
+    // Refresh geometry derived from SysStaff vertical positions.
+    SystemLayout::layoutBracketsVertical(system, ctx);
+    SystemHeaderLayout::setInstrumentNamesVerticalPos(system, ctx);
 }
 
 void SystemLayout::setMeasureHeight(System* system, double height, const LayoutContext& ctx)