test: verify all factual answers work with checkAnswer, fix 2 data bugs

- Hash rate question: added ×10^20 notation to answers array
- Phishing question: added correct MC choice text to answers array
- New tests: self-match, case-insensitive, MC correctness validation

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

server/src/engine/answers.test.ts

@@ -1,5 +1,7 @@
 import { describe, it, expect } from 'vitest'
 import { checkAnswer } from './answers.js'
+import { TEMPLATES } from './challenge-data.js'
+import { EXTRA_PROMPTS } from './challenges-extra.js'
 
 describe('checkAnswer', () => {
   // --- Tier 1: exact match after normalization ---
@@ -146,6 +148,59 @@ describe('checkAnswer', () => {
   })
 })
 
+describe('all factual prompt answers work with checkAnswer', () => {
+  // Merge extras into templates (same as challenges.ts does)
+  const templates = TEMPLATES.map(t => {
+    const extras = EXTRA_PROMPTS[t.type]
+    return extras ? { ...t, prompts: [...t.prompts, ...extras] } : t
+  })
+
+  const factualTemplates = templates.filter(t => t.scoring === 'factual')
+
+  it('every factual prompt has at least one answer', () => {
+    for (const t of factualTemplates) {
+      for (const p of t.prompts) {
+        expect(p.answers, `${t.type}: "${p.prompt}" has no answers`).toBeTruthy()
+        expect(p.answers!.length, `${t.type}: "${p.prompt}" has empty answers array`).toBeGreaterThan(0)
+      }
+    }
+  })
+
+  it('every answer self-matches with checkAnswer (case-insensitive)', () => {
+    let checked = 0
+    for (const t of factualTemplates) {
+      for (const p of t.prompts) {
+        if (!p.answers) continue
+        for (const answer of p.answers) {
+          const score = checkAnswer(answer, p.answers)
+          expect(score, `${t.type}: answer "${answer}" for "${p.prompt}" should self-match`).toBeGreaterThanOrEqual(0.75)
+          // Also test uppercase variant
+          const upper = checkAnswer(answer.toUpperCase(), p.answers)
+          expect(upper, `${t.type}: UPPER "${answer.toUpperCase()}" should match`).toBeGreaterThanOrEqual(0.75)
+          checked++
+        }
+      }
+    }
+    expect(checked).toBeGreaterThan(100)
+  })
+
+  it('MC choices always include the correct answer', () => {
+    let checked = 0
+    for (const t of factualTemplates) {
+      for (const p of t.prompts) {
+        if (!p.choices || !p.answers) continue
+        // At least one choice should match at least one answer
+        const hasCorrect = p.choices.some(choice =>
+          checkAnswer(choice, p.answers!) > 0
+        )
+        expect(hasCorrect, `${t.type}: "${p.prompt}" choices ${JSON.stringify(p.choices)} don't include correct answer ${JSON.stringify(p.answers)}`).toBe(true)
+        checked++
+      }
+    }
+    expect(checked).toBeGreaterThan(50)
+  })
+})
+
 describe('checkAnswer performance', () => {
   it('completes 1000 checks in under 50ms (<0.05ms each)', () => {
     const answers = ['Paris', 'London', 'Tokyo']