Function collapse_cycles 

pub fn collapse_cycles(log: &str) -> String

Collapse repeating cycles in a verifier log.

Runs cycle detection iteratively (up to 5 passes for nested loops). Each cycle is replaced with:

• --- Nx of the following M lines --- (count header, no closing marker)
• first iteration (with original register annotations)
• --- K identical iterations omitted --- (omission marker)
• last iteration (with original register annotations)
• --- end repeat --- (closes the omission)