select-models

arc-skills is the base install. Every other arc-* system (arc-agents, arc-webui, pipeliner) needs to know which two models to use: a fast one for cheap high-volume work and a smart one for the few high-stakes steps. This skill discovers what's available on the machine, lets the user choose, validates each pick by running it, then registers both inside the single source of truth — arc-agents/config.json:

// ~/repos/arc-agents/config.json (after running this skill)
{
  "exec_cli_alias": {
    "opus-max":      "claude --model opus --effort max {prompt}",
    "minimax-fast":  "pi -p --provider minimax --model MiniMax-M2.7 --thinking low {prompt}",
    // ...other aliases unchanged
  },
  "fast_alias":  "minimax-fast",   // <- set by this skill
  "smart_alias": "opus-max",       // <- set by this skill
  "pool_caps":     { /* unchanged */ },
  "default_alias": "minimax-build" // unchanged
}