Function format_timeline 

pub fn format_timeline(recipe: &[(u64, u64)]) -> String

Format a recipe as a human-readable timeline string.

Each segment is formatted as count@seed, joined by ->.

Example

use moonpool_explorer::format_timeline;

let recipe = vec![(42, 12345), (17, 67890)];
assert_eq!(format_timeline(&recipe), "42@12345 -> 17@67890");