fix use-after-free on repl

src/main.zig

@@ -60,9 +60,11 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: anytype) !void {
         var scri_existing = try allocator.alloc(u8, total_bytes);
         _ = try file_read_opt.?.read(scri_existing);
 
-        // we can defer this because we copy the Command structs back to cmds
+        // we can't defer this directly because we copy the
+        // Command pointers to the cmds list. running deinit() directly
+        // would cause those pointers to be freed.
         var existing_cmds = try lang.parse(scri_existing);
-        defer existing_cmds.deinit();
+        defer existing_cmds.list.deinit();
 
         // copy the existing command list into the repl's command list
         for (existing_cmds.list.items) |existing_cmd| {