Fix and() bug and add Swiss loop safety guard

- cs2-major-stage.ts: markCs2StageEliminations and setCs2FinalPlacements
  were using JS && instead of Drizzle and(), causing WHERE to filter only
  by participantId (not scoringEventId), which would update rows across
  all events instead of just the target event
- cs-major-simulator.ts: add break guard in simulateSwiss while loop to
  prevent infinite loop if pairGroups returns no pairs

https://claude.ai/code/session_019w21Nkf5TvTZHH6oVHaQXR

app/models/cs2-major-stage.ts

@@ -14,7 +14,7 @@
 
 import { database } from "~/database/context";
 import { cs2MajorStageResults, participants } from "~/database/schema";
-import { eq, inArray, sql } from "drizzle-orm";
+import { eq, and, inArray, sql } from "drizzle-orm";
 
 export interface Cs2StageResult {
   id: string;
@@ -157,10 +157,10 @@ export async function markCs2StageEliminations(
           stageEliminatedWins: winsAtElimination,
           updatedAt: now,
         })
-        .where(
-          eq(cs2MajorStageResults.scoringEventId, scoringEventId) &&
+        .where(and(
+          eq(cs2MajorStageResults.scoringEventId, scoringEventId),
           eq(cs2MajorStageResults.participantId, participantId)
-        )
+        ))
     )
   );
 }
@@ -184,10 +184,10 @@ export async function setCs2FinalPlacements(
       db
         .update(cs2MajorStageResults)
         .set({ finalPlacement: placements[participantId], updatedAt: now })
-        .where(
-          eq(cs2MajorStageResults.scoringEventId, scoringEventId) &&
+        .where(and(
+          eq(cs2MajorStageResults.scoringEventId, scoringEventId),
           eq(cs2MajorStageResults.participantId, participantId)
-        )
+        ))
     )
   );
 }

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

@@ -193,6 +193,10 @@ export function simulateSwiss(teams: TeamWithElo[], bo3: boolean): SwissResult {
     // (simplified: skip teams that can't be paired — they sit out this round)
     const pairs = pairGroups(groups);
 
+    // Safety: if no pairs can be formed (shouldn't happen with even team counts
+    // but guards against an infinite loop if an odd active count somehow occurs)
+    if (pairs.length === 0) break;
+
     for (const [t1, t2] of pairs) {
       const e1 = eloMap.get(t1.id) ?? FALLBACK_ELO;
       const e2 = eloMap.get(t2.id) ?? FALLBACK_ELO;