# Callback Methods Removal: Complete Migration to Embedded Statistics

## Achievement: Removed All Callback Methods

Following Step 2.4 implementation, we completed the migration from callback-based statistics collection to embedded statistics in solutions, eliminating the need for callback methods entirely.

### Removed Methods:
- `solve_with_callback` - Replaced by embedded `solution.stats` field
- `minimize_with_callback` - Replaced by embedded statistics in `minimize()`
- `minimize_and_iterate_with_callback` - Replaced by embedded statistics in iterator
- `maximize_with_callback` - Replaced by embedded statistics in `maximize()`
- `maximize_and_iterate_with_callback` - Replaced by embedded statistics in iterator
- `find_all_with_callback` - Replaced by embedded statistics in `find_all()`

### Migration Benefits:
- **Simplified API** - No more callback parameters or lambda functions ✅
- **Embedded Statistics** - Every solution includes `.stats` with propagation/node counts ✅
- **Better Performance** - No function call overhead for statistics collection ✅
- **Cleaner Code** - Direct access to statistics without callback management ✅

### Migration Pattern:
```rust
// OLD: Callback-based approach
model.solve_with_callback(|stats| {
    println!("Propagations: {}", stats.propagation_count);
});

// NEW: Embedded statistics approach  
let solution = model.solve()?;
println!("Propagations: {}", solution.stats.propagation_count);
```

This ensures all solving methods provide consistent, embedded statistics without the complexity of callback management.
