feat: convert all human fights to multiple choice, remove text input

Creative challenges (roast_battle, creative_writing, meme_war,
code_golf, wrestling_match) now auto-generate multiple choice options
from per-type response pools: 1 good answer + 3 weaker distractors.
The free text input UI is commented out but preserved for future use.

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

server/src/engine/orchestrator.ts

@@ -250,7 +250,7 @@ async function getBotResponse(
       type: challenge.type,
       label: challenge.label,
       prompt: challenge.prompt,
-      timeoutMs: 8000,
+      timeoutMs: challenge.timeout_ms,
       scoring: challenge.scoring,
     })
     const start = Date.now()