refactor(bench): remove excess whitespace in benchmark progress output

Removed newline prefix from each benchmark status line.
This eliminates blank lines between benchmarks.

Before:
Benchmarking 'Split all' ... ✓

Benchmarking 'Split last index' ... ✓

Benchmarking 'Join' ... ✓

After:
Benchmarking 'Split all' ... ✓
Benchmarking 'Split last index' ... ✓
Benchmarking 'Join' ... ✓

Author: claude

src/bin/bench_throughput.rs

@@ -823,7 +823,7 @@ fn main() {
     let mut all_results = Vec::new();
 
     for (template_name, template_str) in &templates {
-        print!("\nBenchmarking '{}' ... ", template_name);
+        print!("Benchmarking '{}' ... ", template_name);
         std::io::Write::flush(&mut std::io::stdout()).unwrap();
 
         match benchmark_template(template_name, template_str, &sizes, iterations, detailed) {