[codex] Use tuple effect constructor arguments

[briancavalier]

Summary

• refactor Effect(id)<Arg, Answer> to Effect(id)<ArgsTuple, Answer> while keeping inherited of(...) constructors
• pack constructor args as void for zero args, the value for one arg, and a readonly tuple for multi-arg effects
• refactor ScopedEffect to preserve scope as the first constructor argument and use tuple args for the operation payload
• migrate existing effect declarations, zero-arg scoped construction sites, docs, and examples including the guessing game
• extend source and package-import inference tests for zero-, one-, and multi-arg constructor behavior

Notes

This keeps the fine-grained class + union effect model intact. Existing structured payloads remain single constructor arguments; the tuple describes constructor arity rather than redesigning domain payloads. Higher-order or non-trivial smart constructors can still be written explicitly.

Validation

• corepack pnpm build
• corepack pnpm typecheck
• corepack pnpm test
• corepack pnpm lint

Inspected dist/Effect.d.ts; the public constructor signatures show the tuple-based EffectClass and ScopedEffectClass API with internal support aliases.