feat: Update sprint status and complete Epic 2 tasks

- Mark Epic 2 as done and update related stories to reflect completion.
- Add Epic 2 retrospective document detailing team performance, metrics, and insights.
- Enhance draw-relief-icons.ts to include parentEl parameter in drawRelief function.
- Introduce performance measurement scripts for WebGL and SVG rendering comparisons.
- Add benchmarks for geometry building in draw-relief-icons.

src/renderers/draw-relief-icons.bench.ts

@@ -0,0 +1,76 @@
+import { BufferAttribute, BufferGeometry } from "three";
+import { bench, describe } from "vitest";
+import { RELIEF_SYMBOLS } from "../config/relief-config";
+import type { ReliefIcon } from "../modules/relief-generator";
+
+// Standalone geometry harness — mirrors production buildSetMesh() without modifying source.
+// BufferGeometry and BufferAttribute are pure-JS objects; no GPU/WebGL context required.
+function buildSetMeshBench(
+  entries: Array<{ icon: ReliefIcon; tileIndex: number }>,
+  set: string,
+): BufferGeometry {
+  const ids = RELIEF_SYMBOLS[set] ?? [];
+  const n = ids.length || 1;
+  const cols = Math.ceil(Math.sqrt(n));
+  const rows = Math.ceil(n / cols);
+  const positions = new Float32Array(entries.length * 4 * 3);
+  const uvs = new Float32Array(entries.length * 4 * 2);
+  const indices = new Uint32Array(entries.length * 6);
+  let vi = 0;
+  let ii = 0;
+  for (const { icon: r, tileIndex } of entries) {
+    const col = tileIndex % cols;
+    const row = Math.floor(tileIndex / cols);
+    const u0 = col / cols;
+    const u1 = (col + 1) / cols;
+    const v0 = row / rows;
+    const v1 = (row + 1) / rows;
+    const x0 = r.x;
+    const x1 = r.x + r.s;
+    const y0 = r.y;
+    const y1 = r.y + r.s;
+    const base = vi;
+    positions.set([x0, y0, 0], vi * 3);
+    uvs.set([u0, v0], vi * 2);
+    vi++;
+    positions.set([x1, y0, 0], vi * 3);
+    uvs.set([u1, v0], vi * 2);
+    vi++;
+    positions.set([x0, y1, 0], vi * 3);
+    uvs.set([u0, v1], vi * 2);
+    vi++;
+    positions.set([x1, y1, 0], vi * 3);
+    uvs.set([u1, v1], vi * 2);
+    vi++;
+    indices.set([base, base + 1, base + 3, base, base + 3, base + 2], ii);
+    ii += 6;
+  }
+  const geo = new BufferGeometry();
+  geo.setAttribute("position", new BufferAttribute(positions, 3));
+  geo.setAttribute("uv", new BufferAttribute(uvs, 2));
+  geo.setIndex(new BufferAttribute(indices, 1));
+  return geo;
+}
+
+function makeIcons(n: number): Array<{ icon: ReliefIcon; tileIndex: number }> {
+  return Array.from({ length: n }, (_, i) => ({
+    icon: {
+      i,
+      href: "#relief-mount-1",
+      x: (i % 100) * 10,
+      y: Math.floor(i / 100) * 10,
+      s: 8,
+    },
+    tileIndex: i % 9,
+  }));
+}
+
+describe("draw-relief-icons geometry build benchmarks", () => {
+  bench("buildSetMesh — 1,000 icons (NFR-P1 proxy)", () => {
+    buildSetMeshBench(makeIcons(1000), "simple");
+  });
+
+  bench("buildSetMesh — 10,000 icons (NFR-P2 proxy)", () => {
+    buildSetMeshBench(makeIcons(10000), "simple");
+  });
+});

src/renderers/draw-relief-icons.ts

@@ -243,7 +243,7 @@ window.rerenderReliefIcons = () => {
 };
 
 declare global {
-  var drawRelief: (type?: "svg" | "webGL") => void;
+  var drawRelief: (type?: "svg" | "webGL", parentEl?: HTMLElement) => void;
   var undrawRelief: () => void;
   var rerenderReliefIcons: () => void;
 }