fail quickly and more quietly when a single word command is attempted

src/main.zig

@@ -281,6 +281,11 @@ pub fn main() !u8 {
         try stderr.print("Usage: {s} [--sentence-parse-only] [--command-parse-only] <sentence>\n", .{args[0]});
         return 1;
     }
+    if (sentence_parse_only == .none and std.mem.count(u8, sentence_arg.?, " ") == 0) {
+        // a command cannot be made from a single word
+        try stdout.print("Ignoring attempt at single word command\n", .{});
+        return 0;
+    }
     const bin_dir = std.fs.selfExeDirPathAlloc(allocator) catch |err| {
         stderr.print("Failed to get binary path: {}\n", .{err}) catch {};
         return 1;