Fix oxlint violations in CS Major simulator

- Replace non-null assertion (!) with null-safe guard in simulateOneMajor
- Replace non-null assertions in test expectations with nullish coalescing
- Move makeStage3QPConfig out of describe block (no captured variables)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/services/simulations/__tests__/cs-major-simulator.test.ts

@@ -319,9 +319,8 @@ describe("simulateChampionsStage", () => {
 
 // ─── calcStage3ExitQP ─────────────────────────────────────────────────────────
 
-describe("calcStage3ExitQP", () => {
-  function makeStage3QPConfig(): Map<number, number> {
 // Placements 9–16 with descending QP: 9→80, 10→70, ..., 16→10
+function makeStage3QPConfig(): Map<number, number> {
   const config = new Map<number, number>();
   for (let i = 9; i <= 16; i++) {
     config.set(i, (17 - i) * 10);
@@ -329,6 +328,7 @@ describe("calcStage3ExitQP", () => {
   return config;
 }
 
+describe("calcStage3ExitQP", () => {
   it("returns empty map for empty input", () => {
     const result = calcStage3ExitQP([], new Map());
     expect(result.size).toBe(0);
@@ -376,8 +376,11 @@ describe("calcStage3ExitQP", () => {
     const config = makeStage3QPConfig();
     const result = calcStage3ExitQP(elim, config);
 
-    expect(result.get("high")!).toBeGreaterThan(result.get("mid")!);
-    expect(result.get("mid")!).toBeGreaterThan(result.get("low")!);
+    const highQP = result.get("high") ?? 0;
+    const midQP  = result.get("mid")  ?? 0;
+    const lowQP  = result.get("low")  ?? 0;
+    expect(highQP).toBeGreaterThan(midQP);
+    expect(midQP).toBeGreaterThan(lowQP);
   });
 });
 

app/services/simulations/cs-major-simulator.ts

@@ -736,7 +736,8 @@ export function simulateOneMajor(
   const byPlacement = new Map<number, string[]>();
   for (const [pid, placement] of champResult.placements) {
     if (!byPlacement.has(placement)) byPlacement.set(placement, []);
-    byPlacement.get(placement)!.push(pid);
+    const group = byPlacement.get(placement);
+    if (group) group.push(pid);
   }
   for (const [placement, pids] of byPlacement) {
     const slots = Array.from({ length: pids.length }, (_, i) => placement + i);