task(E2): arc-row tool for curved seating around stage

frontend/src/plugins/builtin/event-tools/index.ts

@@ -186,6 +186,61 @@ export const tableTool = makePlaceTool('table', 'Tisch', '\u25cb',
 export const stageTool = makePlaceTool('stage', 'Bühne', '\u25ad',
   (x, y, layerId) => seating.createStage(x, y, layerId), 'Bühne');
 
+// ─────────────────────────────────────────────────────────────
+// Arc-Row (Task E2): Reihen entlang Kreisbogen um Bühnenpunkt.
+// Klick 1: Zentrum (Bühne). Drag: Radius + Startwinkel.
+// Klick 2: Endwinkel → Commit.
+// Phasen: 0=Zentrum setzen, 1=Radius+Start, 2=Endwinkel → commit
+// ─────────────────────────────────────────────────────────────
+let arcCenter: Pt | null = null;
+let arcStartPt: Pt | null = null;
+let arcPhase = 0;
+
+export const arcRowTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'arc-row',
+    label: 'Arc-Row',
+    icon: '\u2312',
+    ribbonTab: 'insert',
+    tags: ['basic'],
+    description: 'Bogenreihe: Zentrum, Startpunkt, Endpunkt klicken',
+  },
+  optionsSchema: [
+    { key: 'arcSpacing', label: 'Abstand (cm)', type: 'number', min: 20, max: 200 },
+  ],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      const { layerId } = optsOf(c);
+      const spacing = (c.options.arcSpacing as number | undefined) ?? 50;
+      if (arcPhase === 0) {
+        arcCenter = e.world;
+        arcPhase = 1;
+        ctx.setStatus('Arc-Row: Radius ziehen (Startpunkt)');
+      } else if (arcPhase === 1 && arcCenter) {
+        arcStartPt = e.world;
+        arcPhase = 2;
+        ctx.setStatus('Arc-Row: Endwinkel klicken');
+      } else if (arcPhase === 2 && arcCenter && arcStartPt && c.doc) {
+        const els = seating.createArcRow(arcCenter.x, arcCenter.y, Math.hypot(arcStartPt.x - arcCenter.x, arcStartPt.y - arcCenter.y),
+          (Math.atan2(arcStartPt.y - arcCenter.y, arcStartPt.x - arcCenter.x) * 180) / Math.PI,
+          (Math.atan2(e.world.y - arcCenter.y, e.world.x - arcCenter.x) * 180) / Math.PI,
+          layerId, spacing);
+        c.doc.transact(() => {
+          for (const el of els) c.doc!.addElement(el);
+        });
+        ctx.setStatus(`Arc-Row: ${els.length} Stühle platziert`);
+        arcPhase = 0; arcCenter = null; arcStartPt = null;
+      }
+    },
+    cancel(ctx) {
+      arcPhase = 0; arcCenter = null; arcStartPt = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus('Arc-Row abgebrochen');
+    },
+  },
+};
+
 /** V2-Plugin: Event-Domain (Tasks A4.9 + E1). */
 export const eventToolsV2Plugin: PluginV2 = {
   manifest: {
@@ -197,5 +252,5 @@ export const eventToolsV2Plugin: PluginV2 = {
     category: 'elements',
     enabledByDefault: true,
   },
-  tools: [chairTool, seatingRowToolDrag, seatingBlockToolDrag, tableTool, stageTool],
+  tools: [chairTool, seatingRowToolDrag, seatingBlockToolDrag, tableTool, stageTool, arcRowTool],
 };

frontend/src/services/seatingService.ts

@@ -280,6 +280,47 @@ export class SeatingService {
     return elements;
   }
 
+  /** Create an arc row (curved seating around a center point) — Task E2 */
+  createArcRow(
+    centerX: number,
+    centerY: number,
+    radius: number,
+    startAngleDeg: number,
+    endAngleDeg: number,
+    layerId: string,
+    spacing = 50,
+  ): CADElement[] {
+    const arcLen = Math.abs(endAngleDeg - startAngleDeg) * Math.PI / 180 * radius;
+    const count = Math.max(2, Math.floor(arcLen / spacing));
+    const rowId = `arcrow_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 8)}`;
+    const elements: CADElement[] = [];
+    for (let i = 0; i <= count; i++) {
+      const angle = startAngleDeg + (endAngleDeg - startAngleDeg) * (i / count);
+      const rad = angle * Math.PI / 180;
+      const px = centerX + radius * Math.cos(rad);
+      const py = centerY + radius * Math.sin(rad);
+      elements.push({
+        id: this.generateId(),
+        type: 'chair',
+        layerId,
+        x: px,
+        y: py,
+        width: 45,
+        height: 45,
+        properties: {
+          rotation: angle + 90,
+          fill: '#4a90d9',
+          backrestColor: '#3a7ac9',
+          outlineColor: '#2a5a99',
+          seatType: 'standard',
+          rowIndex: i,
+          rowId,
+        },
+      });
+    }
+    return elements;
+  }
+
   /** Create a table element */
   createTable(x: number, y: number, layerId: string, config: Partial<TableConfig> = {}): CADElement {
     const cfg = { ...DEFAULT_TABLE, ...config };