Add a couple of example programs

[sourcefrog]

I found these helpful when trying this library out on different diffs.

[Copilot]

Pull request overview

This PR adds two example programs to demonstrate the library's functionality when working with different patch formats.

• Adds reproduce.rs example that parses patches from a file or stdin and reprints them
• Adds dump.rs example that parses patches and outputs their debug representation
• Optimizes a test in ast.rs by replacing vec![] with an array literal

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
examples/reproduce.rs	New example program that reads and reprints patches to verify parsing/formatting round-trips
examples/dump.rs	New example program that displays the debug representation of parsed patches for inspection
src/ast.rs	Minor optimization in test code using array literal instead of vec![] macro

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