feat: Daytona PoC paired task runner with OAuth multi-account support

Adds scripts/daytona_poc_runner.py — end-to-end runner that creates
Daytona sandboxes, installs Claude Code, runs a paired baseline+MCP
task, and collects verification results.

Supports two auth modes:
- --auth api-key (default): uses ANTHROPIC_API_KEY or credentials.json
- --auth oauth --account N: uses Claude Max OAuth tokens from
  ~/.claude-homes/accountN/, with automatic token refresh

Also: --list-accounts to show available OAuth accounts and token status.

Author: sjarmak