feat: implement AI Director & Narrative Voting System (Phase 9)

Add complete AI Director system that transforms the survival simulation
into a user-driven interactive story with audience voting.

Backend:
- Add DirectorService for LLM-powered plot generation with fallback templates
- Add VoteManager for dual-channel voting (Twitch + Unity)
- Integrate 4-phase game loop: Simulation → Narrative → Voting → Resolution
- Add vote command parsing (!1, !2, !A, !B) in Twitch service
- Add type-safe LLM output handling with _coerce_int() helper
- Normalize voter IDs for case-insensitive duplicate prevention

Unity Client:
- Add NarrativeUI for cinematic event cards and voting progress bars
- Add 7 new event types and data models for director/voting events
- Add delayed subscription coroutine for NetworkManager timing
- Sync client timer with server's remaining_seconds to prevent drift

Documentation:
- Update README.md with AI Director features, voting commands, and event types

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

unity-client/Assets/Scripts/NarrativeUI.cs.meta

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