Adds Vast.ai as a new cloud provider (GPU marketplace with per-hour pricing).
Implements vastai/lib/common.sh with provider primitives using the vastai CLI,
and adds 3 initial agent scripts (claude, aider, codex). Remaining 11 agents
added as "missing" matrix entries.
Agent: cloud-scout
Co-authored-by: B <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>