Well, this is from the Catechism that you linked me to,
2008 The merit of man before God in the Christian life arises from the fact that God has freely chosen to associate man with the work of his grace. The fatherly action of God is first on his own initiative, and then follows man's free acting through his collaboration, so that the merit of good works is to be attributed in the first place to the grace of God, then to the faithful. Man's merit, moreover, itself is due to God, for his good actions proceed in Christ,(emphasis added) from the predispositions and assistance given by the Holy Spirit.
2011 The charity of Christ is the source in us of all our merits before God. Grace, by uniting us to Christ in active love, ensures the supernatural quality of our acts and consequently their merit before God and before men. The saints have always had a lively awareness that their merits were pure grace.
If it is all grace then it is not the believer doing the work, it is God doing it and the believer only gets the benefits for it.
The only role that the believer plays in the 'walk' is 'yielding' to God, but he is adding nothing to faith, but is yielding by faith.
However, the passage does not conclude that the believer is "adding nothing to faith" as you claim; it says the opposite, that man is freely collaborating with grace. These are relevant paragraphs also:
1993 Justification establishes cooperation between God's grace and man's freedom. On man's part it is expressed by the assent of faith to the Word of God, which invites him to conversion, and in the cooperation of charity with the prompting of the Holy Spirit who precedes and preserves his assent:[...]
2001 The preparation of man for the reception of grace is already a work of grace. This latter is needed to arouse and sustain our collaboration in justification through faith, and in sanctification through charity. God brings to completion in us what he has begun, "since he who completes his work by cooperating with our will began by working so that we might will it:"50
- Indeed we also work, but we are only collaborating with God who works, for his mercy has gone before us. It has gone before us so that we may be healed, and follows us so that once healed, we may be given life; it goes before us so that we may be called, and follows us so that we may be glorified; it goes before us so that we may live devoutly, and follows us so that we may always live with God: for without him we can do nothing.51
2002 God's free initiative demands man's free response, for God has created man in his image by conferring on him, along with freedom, the power to know him and love him. The soul only enters freely into the communion of love. God immediately touches and directly moves the heart of man. He has placed in man a longing for truth and goodness that only he can satisfy. The promises of "eternal life" respond, beyond all hope, to this desire:
- If at the end of your very good works . . ., you rested on the seventh day, it was to foretell by the voice of your book that at the end of our works, which are indeed "very good" since you have given them to us, we shall also rest in you on the sabbath of eternal life.52
(GRACE)