075 effect branch inside terminal body

// Test: effect branch fired from inside the terminal-return code.
//
// Producer fires `progress(i)` from within the loop, then fires
// `progress(end)` ONE MORE TIME just before returning the terminal.
// Proves an effect call right next to the `return .{ .done = ... };`
// works — they're just Zig statements in the proc body, but it's worth
// verifying since the doc lists this as an open question (#3).

~import std/io

~pub event work { steps: usize }
! progress usize
| done usize

~proc work|zig {
    var i: usize = 0;
    while (i < steps) : (i += 1) {
        progress(i);
    }
    progress(steps); // final emission RIGHT BEFORE the terminal return
    return .{ .done = steps };
}

~work(steps: 2)
! progress p |> std/io:print.blk {
    progress {{ p:d }}
}
| done total |> std/io:print.blk {
    done {{ total:d }}
}