fix(agentrouter): infer protocol from client endpoint
- /v1/responses resolves AgentRouter as openai-responses
- /v1/chat/completions resolves AgentRouter as openai
- /v1/messages resolves AgentRouter as claude
- Per-request protocol and credential cloning (no SQLite mutation)
- Codex 0.146.0 and Claude Code 2.1.220 identity alignment
- response.completed.usage.total_tokens normalization for strict Codex clients
Closes#9224