termio/exec: pass code and runtime to error but don't show it yet

src/termio/Exec.zig

@@ -816,7 +816,10 @@ fn processExit(
         // Notify our main writer thread which has access to more
         // information so it can show a better error message.
         _ = ev.writer_mailbox.push(.{
-            .child_exited_abnormally = {},
+            .child_exited_abnormally = .{
+                .code = code,
+                .runtime_ms = runtime,
+            },
         }, .{ .forever = {} });
         ev.writer_wakeup.notify() catch break :runtime;
 

src/termio/message.zig

@@ -66,7 +66,10 @@ pub const Message = union(enum) {
     /// as process exited but the surface hasn't been notified to
     /// close because termio can use this to update the terminal
     /// with an error message.
-    child_exited_abnormally: void,
+    child_exited_abnormally: struct {
+        code: u32,
+        runtime_ms: u64,
+    },
 
     /// Write where the data fits in the union.
     write_small: WriteReq.Small,