effect-v4-idioms

Use when writing core Effect v4 code — generators (Effect.gen/Effect.fn), typed error handling and recovery (catch/catchTag/catchFilter/catchReason), yieldable errors, PlatformError on FileSystem/Path IO, Cause inspection, Scope and resource cleanup, forking and fibers, runtime/entrypoints, FiberRef-as-Context.Reference, structural equality, Config.schema inputs (a JSON-string input is Config.schema(Schema.fromJsonString(S)), and what withDefault does and does not swallow), and polling with Effect.repeat options instead of a recursive Effect.sleep. Teaches the idiomatic v4 spelling.