feat(twentyq): add reverse-Akinator yes/no game module powered by Workers AI

- seeded 54 objects across 6 categories (instrument, animal, food, vehicle, sport, household)
- @cf/google/gemma-4-26b-a4b-it judges via function calling; returns {is_guess, answer, hint}
- pre-AI validator rejects open-ended questions; handler dedups exact repeats
- secret-redacting hint filter as defense-in-depth
- 86 new vitest tests (seeds, state, validator, ai-client, handlers, render)

tests/modules/twentyq/validate-input.test.js

@@ -0,0 +1,65 @@
+import { describe, expect, it } from "vitest";
+import { validateQuestion } from "../../../src/modules/twentyq/validate-input.js";
+
+describe("twentyq/validate-input", () => {
+  it.each([
+    "is it big?",
+    "are they common?",
+    "does it have wheels?",
+    "do you eat it?",
+    "can it fly?",
+    "has it ever lived?",
+    "have you ridden one?",
+    "was it invented in Asia?",
+    "were they wooden?",
+    "will it float?",
+    "should I include it?",
+    "could you carry it?",
+    "would it fit in a bag?",
+  ])("accepts yes/no opener: %s", (q) => {
+    const r = validateQuestion(q);
+    expect(r.ok).toBe(true);
+    if (r.ok) expect(r.normalized).toBe(q);
+  });
+
+  it.each([
+    "what is it?",
+    "How does it work?",
+    "why is the sky blue?",
+    "which one is it?",
+    "who made it?",
+    "where does it live?",
+    "when was it invented?",
+    "tell me a hint",
+    "describe it",
+    "explain why",
+  ])("rejects open-ended: %s", (q) => {
+    const r = validateQuestion(q);
+    expect(r.ok).toBe(false);
+    if (!r.ok) expect(r.reason).toMatch(/yes\/no/i);
+  });
+
+  it("rejects empty", () => {
+    expect(validateQuestion("").ok).toBe(false);
+  });
+
+  it("rejects too short", () => {
+    expect(validateQuestion("a").ok).toBe(false);
+  });
+
+  it("rejects too long (>200)", () => {
+    expect(validateQuestion("is it ".repeat(80)).ok).toBe(false);
+  });
+
+  it("rejects non-string input", () => {
+    expect(validateQuestion(undefined).ok).toBe(false);
+    expect(validateQuestion(null).ok).toBe(false);
+    expect(validateQuestion(42).ok).toBe(false);
+  });
+
+  it("collapses internal whitespace", () => {
+    const r = validateQuestion("  is   it    big? ");
+    expect(r.ok).toBe(true);
+    if (r.ok) expect(r.normalized).toBe("is it big?");
+  });
+});