- Put `@MainActor` on the whole type once rather than hopping to the main queue inside each callback body. The compiler then proves the thing all those dispatch calls were only hoping for.
- Let a failing function `throw` rather than return `Result`. Callers spend one `try` instead of a switch, and the rare place that must store an outcome wraps the call in `Result { }`.
- Never hand-write `==` or `hash(into:)`. Declare the conformance and let synthesis read the stored properties; when synthesis is wrong the bug is the property list, not the operator.
- Put custom initializers in an extension so the free memberwise init survives, and leave types internal until another module calls them, because `public` withdraws that init too.
- Take `some Protocol` in the parameter list instead of opening a generic clause. Angle brackets earn their keep when two parameters share the type, not before.