Setup Effect toolchain

Four layers, each owning its own diagnostics:

• Typecheck: TypeScript 7 (native tsc) patched by @effect/tsgo, so tsc also reports Effect mistakes such as a floating Effect.
• Lint: Oxlint with oxlint-plugin-effect (effect/*), @shekohex/oxc-effect (effect-shape/*), the local anti-slop plugin (anti-slop/*, anti-slop-effect/*), and type-aware typescript/* rules through oxlint-tsgolint.
• Format: oxfmt with the ultracite preset.
• Runner: ultracite check runs format check and lint in one command.

Which tool owns which diagnostic, and why most anti-slop rules stay off, lives in rule-ownership.md. Read it before changing any rule.

Steps

1. Inspect

Read the repo's agent instructions and git status; leave unrelated changes alone. Decide each branch and state it in your reply: