Macro test_structured 

macro_rules! test_structured {
    ($ctx:expr, $msg:expr) => { ... };
    ($ctx:expr, $msg:expr, $($key:ident = $value:expr),+ $(,)?) => { ... };
}

Emit a structured tracing event with standard test context fields.

Includes test_id, seed, subsystem, and invariant from a TestContext.

let ctx = TestContext::new("my_test", 0xDEAD_BEEF).with_subsystem("scheduler");
test_structured!(ctx, "task spawned", task_count = 5);