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/common/mod.rs

@@ -0,0 +1,36 @@
+#![allow(dead_code)]
+
+use nalgebra::DMatrix;
+
+use dyna3::engine::{Q, DescentHistory, RealizationResult};
+
+pub fn print_title(title: &str) {
+    println!("─── {title} ───");
+}
+
+pub fn print_realization_diagnostics(realization_result: &RealizationResult) {
+    let RealizationResult { result, history } = realization_result;
+    println!();
+    if let Err(ref msg) = result {
+        println!("❌️ {msg}");
+    } else {
+        println!("✅️ Target accuracy achieved!");
+    }
+    println!("Steps: {}", history.scaled_loss.len() - 1);
+    println!("Loss: {}", history.scaled_loss.last().unwrap());
+}
+
+pub fn print_gram_matrix(config: &DMatrix<f64>) {
+    println!("\nCompleted Gram matrix:{}", (config.tr_mul(&*Q) * config).to_string().trim_end());
+}
+
+pub fn print_config(config: &DMatrix<f64>) {
+    println!("\nConfiguration:{}", config.to_string().trim_end());
+}
+
+pub fn print_loss_history(history: &DescentHistory) {
+    println!("\nStep │ Loss\n─────┼────────────────────────────────");
+    for (step, scaled_loss) in history.scaled_loss.iter().enumerate() {
+        println!("{:<4} │ {}", step, scaled_loss);
+    }
+}