perf: reuse clean room areas in PDF

Issue: #53
User-Visible: no

src/houseplan-card.ts

@@ -10690,6 +10690,7 @@ export class HouseplanCard extends LitElement {
     }
     const sharedWallGeometry = this._wallUnionGeometry();
     const openCuts = this._openCuts();
+    const roomsById = new Map(space.rooms.flatMap((room) => room.id ? [[room.id, room]] : []));
     return runtime.render({
       config: this._serverCfg,
       rawSpace,
@@ -10705,6 +10706,10 @@ export class HouseplanCard extends LitElement {
       resolveInnerContour: (roomId) => this._innerRoomContour(
         space, roomId, openCuts, sharedWallGeometry?.roomGeom, sharedWallGeometry?.multiWallNodes,
       ),
+      resolveRoomArea: (roomId, contour) => {
+        const room = roomsById.get(roomId);
+        return room ? this._cleanFloor(room, contour, space).area : undefined;
+      },
       t: (key, vars) => this._t(key as I18nKey, vars),
       toast: (message) => this._showToast(message),
       close: () => { this._pdfDialog = false; this.requestUpdate(); },

src/pdf/hp-pdf-dialog.ts

@@ -19,6 +19,7 @@ export interface PdfDialogContext {
   decorAssets: ReadonlyMap<string, PdfAssetReference>;
   sharedWallGeometry?: PdfSharedWallGeometry | null;
   resolveInnerContour?: (roomId: string) => number[][] | null | undefined;
+  resolveRoomArea?: (roomId: string, contour: number[][]) => number | undefined;
   t: (key: string, vars?: Record<string, string | number>) => string;
   toast: (message: string) => void;
   close: () => void;

src/pdf/pdf-scene.ts

@@ -70,6 +70,8 @@ export interface PdfSceneInput {
   sharedWallGeometry?: PdfSharedWallGeometry | null;
   /** The visible card's per-room clean-floor cache, resolved only when dimensions are requested. */
   resolveInnerContour?: (roomId: string) => number[][] | null | undefined;
+  /** Area in render units from the same clean-floor cache used by the visible card. */
+  resolveRoomArea?: (roomId: string, contour: number[][]) => number | undefined;
 }
 
 const MM = 72 / 25.4;
@@ -383,11 +385,15 @@ export function buildPdfPage(input: PdfSceneInput): PdfPage & { scale: number }
     const original = roomPoly(room);
     if (!original) continue;
     const contour = dimensionContours.get(room) || original;
-    const localBodies = input.options.dimensions
+    const cachedArea = input.options.dimensions && room.id
+      ? input.resolveRoomArea?.(room.id, contour) : undefined;
+    const localBodies = input.options.dimensions && !Number.isFinite(cachedArea)
       ? bodiesOverlappingRing(contour, built.extras) : [];
     const candidates = localBodies.length ? floorMinusBodies(contour, localBodies) : null;
-    const areaUnits = candidates ? geometryArea(candidates) : Math.abs(
-      contour.reduce((sum, p, i) => { const q = contour[(i + 1) % contour.length]; return sum + p[0] * q[1] - q[0] * p[1]; }, 0) / 2);
+    const areaUnits = Number.isFinite(cachedArea) && (cachedArea as number) >= 0
+      ? cachedArea as number
+      : candidates ? geometryArea(candidates) : Math.abs(
+        contour.reduce((sum, p, i) => { const q = contour[(i + 1) % contour.length]; return sum + p[0] * q[1] - q[0] * p[1]; }, 0) / 2);
     const label = labelPos(room, input.space.id, input.layout, input.config);
     const [labelX, labelY] = pt([label.x, label.y]);
     const pageContour = contour.map(pt);