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.

scripts/perf-ac7-sweep.mjs

@@ -0,0 +1,59 @@
+// AC7 detailed icon count comparison
+import {chromium} from "playwright";
+
+async function measure() {
+  const browser = await chromium.launch({headless: true});
+  const page = await browser.newPage();
+
+  await page.goto("http://localhost:5173/Fantasy-Map-Generator/?seed=test-seed&width=1280&height=720");
+  await page.waitForFunction(() => window.mapId !== undefined, {timeout: 90000});
+  await page.waitForTimeout(2000);
+
+  await page.evaluate(() => {
+    window.WebGL2LayerFramework.init();
+    if (window.generateReliefIcons) window.generateReliefIcons();
+  });
+  await page.waitForTimeout(500);
+
+  const counts = [1000, 2000, 3000, 5000, 7000];
+  for (const n of counts) {
+    const result = await page.evaluate(
+      count =>
+        new Promise(res => {
+          const full = window.pack.relief;
+          const c = Math.min(count, full.length);
+          if (c < count * 0.5) {
+            res({skip: true, available: c});
+            return;
+          }
+          window.pack.relief = full.slice(0, c);
+          const el = document.getElementById("terrain");
+
+          const tSvg = performance.now();
+          window.drawRelief("svg", el);
+          const svgMs = performance.now() - tSvg;
+
+          el.innerHTML = "";
+          if (window.undrawRelief) window.undrawRelief();
+
+          const tW = performance.now();
+          window.drawRelief("webGL", el);
+          requestAnimationFrame(() => {
+            const wMs = performance.now() - tW;
+            window.pack.relief = full;
+            const pct = svgMs > 0 ? (((svgMs - wMs) / svgMs) * 100).toFixed(1) : "N/A";
+            res({icons: c, svgMs: svgMs.toFixed(2), webglMs: wMs.toFixed(2), reductionPct: pct});
+          });
+        }),
+      n
+    );
+    if (!result.skip) console.log(`n=${n}: ${JSON.stringify(result)}`);
+  }
+
+  await browser.close();
+}
+
+measure().catch(e => {
+  console.error(e.message);
+  process.exit(1);
+});