perf: разбить вычитание лестниц по кадрам (#663)

Issue: #663
User-Visible: no

src/stairs.ts

@@ -247,3 +247,33 @@ export function geometryMinusStairs(
     return geometry;
   }
 }
+
+/**
+ * The summary panel calculates floor area after the first paint. A maximum
+ * size space may contain 250 stairs; clipping all their footprints in one
+ * polyclip call is observably one long main-thread task on slower clients.
+ * Keep the synchronous helper above for ordinary room-sized callers, while
+ * this iterator bounds each background slice and lets the scheduler yield.
+ */
+export function* geometryMinusStairsSteps(
+  source: Geom,
+  stairs: readonly Stair[] | null | undefined,
+  scale = NORM_W,
+  batchSize = 24,
+): Generator<void, Geom, void> {
+  const footprints = stairList(stairs).map((stair) => stairFootprintGeometry(stair, scale));
+  const size = Math.max(1, Math.floor(batchSize));
+  let geometry = source;
+  for (let index = 0; index < footprints.length; index += size) {
+    const batch = footprints.slice(index, index + size);
+    try {
+      geometry = difference(geometry, ...batch);
+    } catch {
+      for (const footprint of batch) {
+        try { geometry = difference(geometry, footprint); } catch { /* skip only the bad record */ }
+      }
+    }
+    yield;
+  }
+  return geometry;
+}

src/summary-panel-metrics.ts

@@ -9,7 +9,7 @@ import { innerContourForRoom, multiWallNodesForGeometry, wallBodiesGeometry } fr
 import type { Marker, ServerConfig, SpaceModel, SummaryPanelSource } from './types';
 import type { HaRegistrySnapshot } from './ha-binding-status';
 import type { SummaryHass } from './summary-panel-host';
-import { geometryMinusStairs } from './stairs';
+import { geometryMinusStairsSteps } from './stairs';
 
 /** Count the unique real HA devices represented anywhere on the plan. */
 export function representedHaDeviceIds(input: {
@@ -119,9 +119,16 @@ export function* cleanFloorAreaSteps(
         spaceFloor = unionGeometry(spaceFloor, clean);
         yield;
       }
-      // Difference distributes over union. Subtracting the shared stair set once
-      // avoids rooms x stairs polygon clips on dense plans (#663).
-      spaceFloor = geometryMinusStairs(spaceFloor || [], space.stairs);
+      // Difference distributes over union. Subtract the shared stair set once,
+      // but in bounded batches: 250 footprints in one polyclip sweep becomes a
+      // visible long task on slower clients (#663).
+      const stairSteps = geometryMinusStairsSteps(spaceFloor || [], space.stairs);
+      let stairStep = stairSteps.next();
+      while (!stairStep.done) {
+        yield;
+        stairStep = stairSteps.next();
+      }
+      spaceFloor = stairStep.value;
       const cmPerUnit = prepared.cellCm / GRID_PITCH;
       total += geometryArea(spaceFloor) * cmPerUnit * cmPerUnit / 1e4;
     }