refactor: one function owns the junction geometry of a space (#229 r2 M1)

Дефект High-1 был одинаковым в двух местах — и в живом рисовании, и в
«Оптимизировать планы», — потому что каждый вызывающий собирал геометрию
примыканий сам. Ревью r2 справедливо заметило, что и защита получилась
однобокой: юнит и мутант сторожили только оптимизатор, а путь карты — тот, где
дефект и был виден пользователю, — не сторожил никто. Заплатка в виде второго
мутанта-близнеца оставила бы причину на месте: два списка координат, которые
обязаны совпадать, но ничем не связаны.

Поэтому геометрия переехала в `spaceMergeGeometry(space, { excludeDraftId })`:
один источник комнат, колонн и концов черновиков, одни координаты, одно место,
где можно ошибиться. Оба вызывающих теперь строчка вызова.

Покрытие идёт за причиной, а не за симптомом: три юнита в
`test/wall-merge.test.mjs` проверяют масштаб полигонов (включая комнаты в форме
x/y/w/h и комнату без геометрии), исключение активного черновика и сам T-стык к
середине стороны комнаты. Мутанты `partition-merge-rescales-rooms` и
`chain-merge-sees-own-draft` перенацелены на общий модуль и теперь краснеют для
обоих путей сразу: 2 и 1 падение, проверено применением патча.

Сценарий с комнатой в смоке пробовал — не взлетел: рисование в комнату
поднимает `_offerWallFaces`, и цепочка не завершается штатно. Ломать смок под
тест не стал, юниты общего модуля покрывают оба пути честнее.

Issue: #229
User-Visible: no

src/houseplan-card.ts

@@ -265,7 +265,7 @@ import {
   applySpaceOrder, canStartTabDrag, markersNeedingPlacement, passedDragThreshold,
   reorderSpaceIds,
 } from './space-order';
-import { applyOpeningMoves, mergeCollinearPartitions } from './wall-merge';
+import { applyOpeningMoves, mergeCollinearPartitions, spaceMergeGeometry } from './wall-merge';
 
 const CARD_VERSION = '1.66.0';
 const DISPLAY_LABEL_KEYS: Record<DeviceDisplayMode, I18nKey> = {
@@ -6548,26 +6548,10 @@ class HouseplanCard extends LitElement {
   private _mergeSpacePartitions(sp: any, seedIds?: string[]): number {
     const partitions = (sp?.partitions || []) as PartitionCfg[];
     if (partitions.length < 2) return 0;
-    const rooms = (sp.rooms || []) as any[];
     const result = mergeCollinearPartitions(partitions, {
       pitch: GRID_STEP_N,
       seedIds,
-      geometry: {
-        // Same coordinates as the partitions — `roomPoly` returns the raw
-        // config polygon (review CODE-REVIEW-229-r1, High-1).
-        roomPolygons: rooms
-          .map((room) => roomPoly(room))
-          .filter((poly): poly is number[][] => !!poly),
-        columns: sp.wall_columns || [],
-        // The chain being finished is still persisted as a draft at this
-        // point, and its own ends must not pass for someone else's junction —
-        // the same exclusion plan-snap-overlay makes (review r1, High-2).
-        draftEnds: (sp.room_drafts || []).flatMap((draft: any) => {
-          if (draft?.id && draft.id === this._activeDraftId) return [];
-          const points = draft?.points || [];
-          return points.length ? [points[0], points[points.length - 1]] : [];
-        }),
-      },
+      geometry: spaceMergeGeometry(sp, { excludeDraftId: this._activeDraftId }),
     });
     if (!result.merged) return 0;
     sp.partitions = result.partitions;

src/plan-optimizer.ts

@@ -24,7 +24,7 @@ import {
   degradeWalls, normalizeWallIntervals, rekeyWallsAfterMove, roomWallProfile,
   setWallThickness, type WallEntry,
 } from './wall-thickness';
-import { applyOpeningMoves, mergeCollinearPartitions } from './wall-merge';
+import { applyOpeningMoves, mergeCollinearPartitions, spaceMergeGeometry } from './wall-merge';
 
 /** Bump when a new lossless maintenance pass is added. */
 export const PLAN_MODEL_VERSION = 6;
@@ -502,20 +502,7 @@ export function optimizePlans(configIn: any, layoutIn: Record<string, any>): Opt
     // plan finally loses them — explicitly, with a report and an undo (#229).
     const partitionMerge = mergeCollinearPartitions(space.partitions || [], {
       pitch: GRID_STEP_N,
-      geometry: {
-        // Rooms are stored in the same coordinates as partitions: `roomPoly`
-        // hands back the raw config polygon, so scaling it here would push
-        // every room into a corner and no junction would ever be found
-        // (review CODE-REVIEW-229-r1, High-1).
-        roomPolygons: (space.rooms || [])
-          .map((room: any) => roomPoly(room))
-          .filter((poly: number[][] | null): poly is number[][] => !!poly),
-        columns: space.wall_columns || [],
-        draftEnds: (space.room_drafts || []).flatMap((draft: any) => {
-          const points = draft?.points || [];
-          return points.length ? [points[0], points[points.length - 1]] : [];
-        }),
-      },
+      geometry: spaceMergeGeometry(space),
     });
     if (partitionMerge.merged) {
       partitionsMerged += partitionMerge.merged;

src/wall-merge.ts

@@ -16,6 +16,7 @@
 
 import type { OpeningCfg, PartitionCfg, WallColumnCfg } from './types';
 import { materializePartitionOpening, resolvePartitionOpeningCompat } from './partition-openings';
+import { roomPoly } from './logic';
 
 /** Collinearity, as a fraction of one grid pitch (spec §8.3). */
 export const EPS_ANGLE = 0.02;
@@ -260,3 +261,35 @@ export function applyOpeningMoves(
   }
   return moved;
 }
+
+/**
+ * The junction geometry of one space, in the coordinates the partitions use.
+ *
+ * Both callers — the live editor and “Optimize plans” — need exactly the same
+ * three things, and when each built them for itself the identical mistake was
+ * made twice: room polygons were scaled a second time and no room junction was
+ * ever found (review CODE-REVIEW-229-r1/r2). One function, one set of
+ * coordinates, one place to get it wrong.
+ *
+ * `excludeDraftId` is the chain being finished right now: it is already
+ * persisted in `room_drafts`, and its own ends are not a foreign junction —
+ * the same exclusion `plan-snap-overlay` makes.
+ */
+export function spaceMergeGeometry(
+  space: any, options?: { excludeDraftId?: string | null },
+): MergeGeometry {
+  const exclude = options?.excludeDraftId || null;
+  return {
+    // `roomPoly` hands back the raw config polygon: rooms are stored in the
+    // same normalised coordinates as partitions, so nothing is rescaled here.
+    roomPolygons: (space?.rooms || [])
+      .map((room: any) => roomPoly(room))
+      .filter((poly: number[][] | null): poly is number[][] => !!poly),
+    columns: space?.wall_columns || [],
+    draftEnds: (space?.room_drafts || []).flatMap((draft: any) => {
+      if (exclude && draft?.id === exclude) return [];
+      const points = draft?.points || [];
+      return points.length ? [points[0], points[points.length - 1]] : [];
+    }),
+  };
+}