cmd: added comment for input validation (per Andrea's pr comment)

Signed-off-by: Sam Alba <sam.alba@gmail.com>

cmd/dagger/cmd/input/root.go

@@ -44,6 +44,7 @@ func updateEnvironmentInput(ctx context.Context, cl *client.Client, target strin
 	st.SetInput(target, input)
 
 	_, err := cl.Do(ctx, st, func(ctx context.Context, env *environment.Environment, s solver.Solver) error {
+		// the inputs are set, check for cue errors by scanning all the inputs
 		_, err := env.ScanInputs(ctx, true)
 		if err != nil {
 			return err