refactor(bench): reduce header and separator width from 110 to 80 chars

Changed the width of all headers and line separators to 80 characters
to better fit standard terminal widths:

- Header boxes: 110 chars → 80 chars (78 '═' chars + 2 for borders)
- Section separators: 110 chars → 80 chars (80 '─' chars)
- Updated padding calculation: (107 - text_width) → (77 - text_width)

This makes the output more readable on standard 80-column terminals.

Author: claude

src/bin/bench_throughput.rs

@@ -399,12 +399,12 @@ fn print_header(text: &str) {
         SetForegroundColor(Color::Cyan),
         SetAttribute(Attribute::Bold),
         Print("╔"),
-        Print("═".repeat(108)),
+        Print("═".repeat(78)),
         Print("╗\n║ "),
         Print(text),
-        Print(" ".repeat(107 - text_width)),
+        Print(" ".repeat(77 - text_width)),
         Print("║\n╚"),
-        Print("═".repeat(108)),
+        Print("═".repeat(78)),
         Print("╝\n"),
         ResetColor
     );
@@ -421,7 +421,7 @@ fn print_section_header(text: &str) {
         ResetColor,
         Print("\n"),
         SetForegroundColor(Color::DarkGrey),
-        Print("─".repeat(110)),
+        Print("─".repeat(80)),
         ResetColor
     );
 }