Update orchestrator scripts to use pi with ben's auth

Update pi-orchestrate.sh, pi-code.sh, pi-review.sh:

• Remove OpenRouter-specific code (--provider openrouter, --api-key)
• Use pi with default auth (ben's ~/.pi tokens)
• This switches from OpenRouter to direct Claude Code API

The scripts currently do: pi -p "$PROMPT" --provider openrouter --model anthropic/claude-opus-4.5 --api-key "$OPENROUTER_API_KEY"

Should become: pi -p "$PROMPT"

(pi will use its default auth from ~/.pi/)