Run an astcount refactor loop

Keep finding and applying readable, behavior-preserving simplifications that reduce Tree-sitter named-node count. Do not stop after the first successful decrease or ask whether to continue merely because candidates succeeded.

Establish the measurement

Infer the scope from the request, defaulting to the repository. Resolve one astcount command, run it with --version, and reuse that exact invocation:

1. When command -v nix succeeds, use nix run github:wokalski/astcount/v0.3.0 --.
2. Otherwise, use bunx astcount@0.3.0 when Bun is available.
3. Otherwise, use npx --yes astcount@0.3.0 when npx is available.
4. Stop if none is available.