threads

Implement basic threads:

// syntax is a to-do, too, a bit
//spawns a new thread with the identifier 'myname'. Thread names are optional
thread myname {
    stuff1();
    stuff2();
    etc();
}

join myname; //joins a thread, no-op if thread has already finished

let x = 5;
let y = 6;

// captures variables for a thread. Currently unsure if it should actually move them or just copy
// Not really sure about syntax here
thread |x, y| {
    print(x);
    print(y);
}

// all threads are joined when the main script thread is about to finish to prevent threads being stopped unexpectedly

No implementation files, entry points, or tests are named. Start by reviewing the proposed thread and join syntax, variable-capture semantics, and main-thread shutdown behavior. Done requires settled syntax and semantics plus implementation and tests covering basic spawning, joining, captures, and automatic final joins.