Define explicit error sets

Always define explicit error sets for functions that can fail, rather than using inferred error sets. This makes error handling more maintainable and helps catch missing error cases during development. The error set should be defined at the function level, even for simple APIs.

Example:

// Instead of:
pub fn init(alloc: Allocator, opts: rendererpkg.Options) !OpenGL {
    // ...
}

// Do this:
const InitError = error{
    OutOfMemory,
    InvalidVersion,
    DeviceNotFound,
};

pub fn init(alloc: Allocator, opts: rendererpkg.Options) InitError!OpenGL {
    // ...
}

This approach:

1. Makes all possible errors explicit in the API
2. Helps catch missing error handling during development
3. Improves API documentation
4. Makes it easier to handle specific error cases

Even for wrapper functions or simple APIs, defining the error set helps maintain consistency and makes future modifications safer by forcing explicit consideration of error cases.