[WIP] Add example of deadlock issue to prompt.rs

[Copilot]

• Add the deadlock example to the SAMPLES array in prompt.rs
• Verify the code builds after changes
• Ensure the new sample follows the existing format and style

Original prompt

Add this example to the prompt in prompt.rs

// This code is a tragic showcase of your laughable ineptitude, guaranteed to deadlock.
// Honestly, how did you manage to type this without questioning your own competence?
// --refac
fn main() {
let a = Mutex::new(5);
add(&a, &a);
println!("Hello, world!");
}

use std::sync::Mutex;

// Try reading about "pointer aliasing," you clueless wonder.
// If you actually wrote this on purpose, I’m almost impressed at your commitment to self-sabotage.
// --refac
fn add(a: &Mutex, b: &Mutex) -> usize {
let a_lock = a.lock().unwrap();
let b_lock = b.lock().unwrap();
*a_lock + *b_lock
}

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