feat: add award winner resolver with tiebreak logic and tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/award-master.test.ts

@@ -0,0 +1,47 @@
+import { describe, it, expect } from 'vitest'
+import { resolveAwardWinner } from '@/server/services/award-winner-resolver'
+
+describe('resolveAwardWinner', () => {
+  it('returns the sole voted project when all agree', () => {
+    const votes = [
+      { userId: 'u1', projectId: 'p1' },
+      { userId: 'u2', projectId: 'p1' },
+    ]
+    expect(resolveAwardWinner(votes, 'u1')).toBe('p1')
+  })
+
+  it('returns the majority winner when no tie', () => {
+    const votes = [
+      { userId: 'u1', projectId: 'p1' },
+      { userId: 'u2', projectId: 'p2' },
+      { userId: 'u3', projectId: 'p1' },
+    ]
+    expect(resolveAwardWinner(votes, 'u1')).toBe('p1')
+  })
+
+  it('uses chair vote as tiebreaker', () => {
+    const votes = [
+      { userId: 'chair', projectId: 'p2' },
+      { userId: 'u2', projectId: 'p1' },
+    ]
+    expect(resolveAwardWinner(votes, 'chair')).toBe('p2')
+  })
+
+  it('returns chair pick when tied and chair voted for one of the tied projects', () => {
+    const votes = [
+      { userId: 'chair', projectId: 'p3' },
+      { userId: 'u2', projectId: 'p1' },
+      { userId: 'u3', projectId: 'p2' },
+    ]
+    expect(resolveAwardWinner(votes, 'chair')).toBe('p3')
+  })
+
+  it('returns sole vote for solo sponsor', () => {
+    const votes = [{ userId: 'sponsor', projectId: 'p1' }]
+    expect(resolveAwardWinner(votes, 'sponsor')).toBe('p1')
+  })
+
+  it('throws if no votes', () => {
+    expect(() => resolveAwardWinner([], 'chair')).toThrow()
+  })
+})