feat: parse and display all optional headers (M2)

Implement parsing for all 15 optional header types found in XEX2 files:
inline values (entry point, base address, stack size, system flags),
fixed-size structures (execution info, file format, TLS, game ratings,
LAN key, checksum/timestamp), and variable-size structures (static
libraries, import libraries, resource info, original PE name, Xbox 360
logo). Add comprehensive unit and integration tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main.rs

@@ -26,4 +26,5 @@ fn main() {
     };
 
     xex2tractor::display::display_header(&xex.header);
+    xex2tractor::display::display_optional_headers(&xex.optional_headers);
 }