Stamp a model-right-sizer mandate onto the CURRENT repo's agent-instructions file — `CLAUDE.md`, `AGENTS.md`, or both, whichever the repo has. Idempotent and append-only: an existing file is never overwritten, only the marker-delimited mandate block is inserted or refreshed. The mandate's "before" hook runs `model-right-sizer-dryrun` to produce a schema-conformant JSON blueprint for the orchestrator to route by. Also checks whether the `model-right-sizer` agent and `model-right-sizer-dryrun` skill are discoverable and, if either is missing, installs the `model-right-sizer` Claude Code plugin to fix that (falling back to manual instructions otherwise). Deliberately narrow and organization-agnostic — installs only the right-sizing mandate (plus its own dependencies, if absent), not any broader development process. Use when someone says "install model-right-sizer in this repo", "init this repo for model-right-sizer", "add the right-sizer mandate here", or "make this repo consult model-right-sizer every turn".