How do Calvinists interpret Acts 7:51 in light of the doctrine of 'irresistible grace?'

R. C. Sproul in his book What is Reformed Theology? says that most of the conventional labels in the TULIP rubric are poorly named, including "Irresistible Grace". He prefers the label The Spirit's Effective Call, which matches the Westminster Confession's 10th chapter. So before I get to Acts 7 and the resistible graces, I'll quickly outline what the doctrine of Effectual Calling is. First from the Westminster Confession:

WCF 10.1: All those whom God hath predestinated unto life, and those only, he is pleased, in his appointed and accepted time, effectually to call, by his word and Spirit, out of that state of sin and death in which they are by nature, to grace and salvation by Jesus Christ: enlightening their minds, spiritually and savingly, to understand the things of God, taking away their heart of stone, and giving unto them an heart of flesh; renewing their wills, and by his almighty power determining them to that which is good; and effectually drawing them to Jesus Christ; yet so as they come most freely, being made willing by his grace.

WCF 10.2: This effectual call is of God's free and special grace alone, not from any thing at all foreseen in man, who is altogether passive therein, until, being quickened and renewed by the Holy Spirit, he is thereby enabled to answer this call, and to embrace the grace offered and conveyed in it.

The 'call' or 'grace' of this doctrine is specifically that of the saving grace and call to life out of death. When God calls the elect they are spiritually dead, with hearts of stone, unable to respond in faith. God must regenerate them for them to be able to respond to him in faith. And it is effective for God does not give us a heart halfway between stone and flesh, but a living heart. Sproul writes:

The call referred to in effectual calling is not the outward call of the gospel that can be heard by anyone within range of the reaching. The call referred to here is the inward call, the call that penetrates to and pierces the heart, quickening it to spiritual life. Hearing the gospel enlightens the mind, yet it does not awaken the soul until the Holy Spirit illumines and regenerates it. The move from ear to soul is made by the Holy Spirit. (p191)

One of the best Biblical images for Effectual Calling is the resurrection of Lazarus. However much Lazarus might have responded to God in faith and obedience, Jesus Christ's calling of his dead body back to life was at the same time entirely effective and entirely external to Lazarus. Lazarus's dead body did not generate a seed of life which God then grew. His dead heart did not kickstart itself, his dead lungs did not gulp down a breath which God then sent to oxygenate the rest of his body through his veins. No, he was dead and the life came from God alone. We see the same idea in Ephesians:

Ephesians 2:1-5 (NIV): As for you, you were dead in your transgressions and sins, in which you used to live when you followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient. All of us also lived among them at one time, gratifying the cravings of our flesh and following its desires and thoughts. Like the rest, we were by nature deserving of wrath. But because of his great love for us, God, who is rich in mercy, made us alive with Christ even when we were dead in transgressions—it is by grace you have been saved.

This calling is called "Irresistible Grace" because the new life Christians are given is irresistible in the same way that we cannot will our hearts to stop beating, or make ourselves hold our breaths forever without breathing. Once God has made us physically alive we cannot help but live. Once God has made us spiritually alive we cannot help but spiritually live, growing closer to God, learning obedience to his will, and carrying out the good works he has prepared for us. Or consider the miracles when Jesus restored the sight of the blind: blind people cannot restore their own sight, but once it has been restored to them they cannot help but see and take in the light around them. Yes we cooperate with his will in faith, but it comes after the regeneration that made dead things into the living children of God.

So what of the resistible graces, calls, and works of the Holy Spirit? The Reformed doctrine of Irresistible Grace is strictly only about the work of the Spirit to bring life to dead people. But the Spirit has many other works, God has many other calls, and he gives us many other graces. All of these can be resisted to various extents:

1. There is the grace of creation and providence given to all things in this universe.
2. There is the work of the Spirit in our consciences convicting us of our sin and calling us away from it.
3. There is the call of God in the Hebrew scriptures to love him and obey his law.
4. There is the call of the incarnate Son of God as he lived amongst his people and preached the Kingdom of God.
5. There is the external call of the gospel preached by the church.

In his sermon in Acts 7 Stephen reminded the Jews of their history alongside God. Just as the patriarchs resisted the God's invitation to have faith despite so many difficult circumstances, and just as the Israelites of the Exodus resisted God's instruction during their wanderings in the wilderness, so too the Jews of Jesus's time resisted his preaching, and then the preaching of the Apostles and early church. Stephen called them to repent of their resistance and to submit to the gospel and the witness of the Holy Spirit.

And even amongst the Jews of the Sanhedrin who executed Stephen, there was (at least) one who God had chosen. But while Saul tried his hardest to resist the work of the Spirit in the preaching of the church, very soon after God would effectually call Saul to life and faith. When Christ revealed the truth of himself to Saul, Saul became incapable of denying that truth. Like a child who realises for the first time that their parents are fallible, when God reveals himself to us the reality of who God is becomes one of our facts. It was the paradigm shift of Saul's life; he had seen reality and his life was indelibly changed.

In the conversion of Saul we see what is true for all Christians: that God calls to life dead souls that cannot bring themselves to love God or have faith in him. This is true for all of us, even though most of us subjectively experience the call of God, the regeneration of the Spirit, and the growing seeds of our faith concurrently.