v0.8.0 - model rotation, kimi-k3, inject, no refusals

Model rotation on failure (2 fails → next fallback, cycles back to primary). Primary switched to moonshotai/kimi-k3 for in-character compliance. max_tokens 32768 in every request. Wall-clock NIM deadline (300s, thread-safe). POST /whatsapp/inject: fire-and-forget full agent turn on any chat. No-refusal instruction for allowlisted groups. Docs in plain prose. Tests: 481 pass, 3 skip. Zig 0.16.0.