feat(examples): add grammar generation and pretty-printing utilities

Add new examples for generating sample .improv data based on the Pest
grammar and pretty-printing existing .improv files.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (gemma-4-31B-it-UD-Q4_K_XL.gguf)

examples/pretty-print.rs

@@ -0,0 +1,25 @@
+//! Parse a `.improv` file from stdin and print the formatted result to stdout.
+//!
+//! Usage:
+//!   cargo run --example pretty-print < file.improv
+//!   cargo run --example gen-grammar -- file | cargo run --example pretty-print
+
+use std::io::Read;
+
+fn main() {
+    let mut input = String::new();
+    if let Err(e) = std::io::stdin().read_to_string(&mut input) {
+        eprintln!("Failed to read stdin: {e}");
+        std::process::exit(1);
+    }
+
+    match improvise::persistence::parse_md(&input) {
+        Ok(model) => {
+            print!("{}", improvise::persistence::format_md(&model));
+        }
+        Err(e) => {
+            eprintln!("Parse error: {e:#}");
+            std::process::exit(1);
+        }
+    }
+}