Encapsulate realization results

In the process, spruce up our realization diagnostics logging and factor
out some of the repetitive code in the examples, because we're already
changing those parts of the code to adapt them to the new encapsulation.

This commit changes the example output format. I've checked by hand that
the output is rearranged but not meaningfully changed.

app-proto/examples/irisawa-hexlet.rs

@@ -1,25 +1,28 @@
-use dyna3::engine::{Q, examples::realize_irisawa_hexlet};
+mod common;
+
+use common::{
+    print_gram_matrix,
+    print_loss_history,
+    print_realization_diagnostics,
+    print_title
+};
+use dyna3::engine::{Realization, examples::realize_irisawa_hexlet};
 
 fn main() {
     const SCALED_TOL: f64 = 1.0e-12;
-    let (config, _, success, history) = realize_irisawa_hexlet(SCALED_TOL);
-    print!("\nCompleted Gram matrix:{}", config.tr_mul(&*Q) * &config);
-    if success {
-        println!("Target accuracy achieved!");
-    } else {
-        println!("Failed to reach target accuracy");
-    }
-    println!("Steps: {}", history.scaled_loss.len() - 1);
-    println!("Loss: {}", history.scaled_loss.last().unwrap());
-    if success {
+    let realization_result = realize_irisawa_hexlet(SCALED_TOL);
+    print_title("Irisawa hexlet");
+    print_realization_diagnostics(&realization_result);
+    if let Ok(Realization { config, .. }) = realization_result.result {
+        // print the diameters of the chain spheres
         println!("\nChain diameters:");
         println!("  {} sun (given)", 1.0 / config[(3, 3)]);
         for k in 4..9 {
             println!("  {} sun", 1.0 / config[(3, k)]);
         }
+        
+        // print the completed Gram matrix
+        print_gram_matrix(&config);
     }
-    println!("\nStep │ Loss\n─────┼────────────────────────────────");
-    for (step, scaled_loss) in history.scaled_loss.into_iter().enumerate() {
-        println!("{:<4} │ {}", step, scaled_loss);
-    }
+    print_loss_history(&realization_result.history);
 }